Free things are not really "free". They come at a cost, here some examples:
 - "Buy 3 and get 2 for free": You clearly paid for the 5, but you will maybe tell your friends about the offer, bringing more people to buy.
 - Youtube: free videos. You watch advertisements, you subscribe, you are the audience that will make more creator using Youtube instead of other platforms, you share videos with your friends, which brings them to Youtube.
 - Facebook: free account. You are giving them data like your interests, likes, so it can be used by advertisers paying Facebook to target people "like you". You invite more friends to join, or people join because you and the rest are already using it.
 - Free samples: they make you more likely to buy the product, mainly if you like it (for some people, even if they don't like it, they may feel like they "have to" buy it because they got some for free)
 - Free eBook: please enter your email and subscribe to out newsletter to receive the free eBook.
 - Free birthday present from a friend of family member, many times, are the reason why you will also buy a present for that person's birthday.
 - Free drink because a friend paid, you better pay the next round
 - Free social services (paid from taxes, probably yours too)
 
Regarding your main question:
How could some profit from the economy of free things, and what would the reaction to this opportunity, by the general public, be?

The "some" who could profit could be the general public themselves, or companies.
I could go broad as I did with the examples above, but I will focus on Cryptocurrency Airdrops, which is the main topic.

 - The reaction by the public is usually good when it comes to free Airdrops. To note that if they don't provide value in return to the project doing the airdrop, less airdrops will happen in future, so the general public can't just take the money and run, as this will only lead to no more airdrops in the future.

 - Getting 5 times more free coins doesn't make you feel 5 times better, which is why projects can get the best results by giving very little per person, getting much more people "on board" resulting in more people contributing by providing value to the project.

 - Projects can profit by getting data from the general public, with their permission, on exchange for the "free" airdrop.

 - Projects can profit from social proof, so they are able to say "we already have 10000 people on our community". However, if the community is not active it is an issue. The project has to find the way to make the community give value on exchange for the free airdrop, more than their email. Their actual attention (who reads emails?) would be enough, so that people learn of the news from the project and get more engaged with time.

I hope that kind of answers the main question, looking forward to see how the debate continues.

Something interesting:
When given the option, would prefer an Iphone 3 for free than an Iphone X for 100 USD.
However, if the Iphone 3 is 5 USD and the Iphone X is 100 USD, most people will choose the iPhone X this time, which is more rational.
Great video in Spanish which shows this happen, with cheap/expensive chocolate: https://youtu.be/xmiL94yx28U?t=10m
The video is for free

Enjoy it.

Castle will be doing a hard fork in some days, releasing Masternodes.

Castle is releasing an Automatic Airdrop Platform for tokens/coins to promote their projects mainly via Airdrops.
Castle CSTL coin holders receive airdrops from those projects. The more CSTL, the bigger is the airdrop quantity.

Worth keeping a look into, some people are already filling their bags up.
Exchanges:
https://stocks.exchange/trade/CSTL/BTC

Website: https://www.projectcastle.tech/
ANN: https://bitcointalk.org/index.php?topic=2454798
Infographic: https://www.projectcastle.tech/img/Castle_Infographic.jpg
White Paper: https://www.projectcastle.tech/White_Paper.pdf
Discord: https://discord.gg/GgHJs8s
Twitter: https://twitter.com/CASTLE_CSTL
Telegram: https://t.me/castle_cstl

Castle will be doing a hard fork in some days, releasing Masternodes.

Castle is releasing an Automatic Airdrop Platform for tokens/coins to promote their projects mainly via Airdrops.
Castle CSTL coin holders receive airdrops from those projects. The more CSTL, the bigger is the airdrop quantity.

Worth keeping a look into, some people are already filling their bags up.
Exchanges:
https://stocks.exchange/trade/CSTL/BTC

Website: https://www.projectcastle.tech/
ANN: https://bitcointalk.org/index.php?topic=2454798
Infographic: https://www.projectcastle.tech/img/Castle_Infographic.jpg
White Paper: https://www.projectcastle.tech/White_Paper.pdf
Discord: https://discord.gg/GgHJs8s
Twitter: https://twitter.com/CASTLE_CSTL
Telegram: https://t.me/castle_cstl

Castle will be doing a hard fork in some days, releasing Masternodes.

Castle is releasing an Automatic Airdrop Platform for tokens/coins to promote their projects mainly via Airdrops.
Castle CSTL coin holders receive airdrops from those projects. The more CSTL, the bigger is the airdrop quantity.

Worth keeping a look into, some people are already filling their bags up.
Exchanges:
https://stocks.exchange/trade/CSTL/BTC

Website: https://www.projectcastle.tech/
ANN: https://bitcointalk.org/index.php?topic=2454798
Infographic: https://www.projectcastle.tech/img/Castle_Infographic.jpg
White Paper: https://www.projectcastle.tech/White_Paper.pdf
Discord: https://discord.gg/GgHJs8s
Twitter: https://twitter.com/CASTLE_CSTL
Telegram: https://t.me/castle_cstl

New wallets are being developed.
Here is the Github: https://github.com/castlec0in

Thanks.

Proof-of-care is still open: https://docs.google.com/forms/d/e/1FAIpQLSfw7GjmRRQsvrW59syljzvsZ-9xy4DBjAY05YLEif8axVcfZQ/viewform?usp=sf_link

ZCL/CSTL Giveaway: https://gleam.io/YJDKv/zcl-giveaway-castle-airdrops-platform

We will soon have an Airdrops Platform which will revolutionise the crypto Airdrops market.
You may want to grab some CSTL on the exchange before that happens!
https://stocks.exchange/trade/CSTL/BTC

Re-installing the wallet and replacing the Wallet.dat file with the one you backed up, on %appdata% folder "Castle".

It costs 40000 CSTL for a Masternode. They will be released anytime, under 2 months.
Castle can be bought here: https://stocks.exchange/trade/CSTL/BTC

For wallet issues, please find a temporary solution on the pinned post of the #support and #wallet channels on our Discord, thanks for your feedback.
https://discord.gg/GgHJs8s

The Devs are working on a new wallet which will not have that known issue.

@nguyenthicamtu
@AndyNguyen1988
@nguyenthithuken

If the mandatory tasks were completed (Join Telegram, join Discord, Provide CSTL Wallet) then you should have received the coins, please PM Juan🏰Castle Airdrops Platform🏰 on Discord (https://discord.gg/GgHJs8s ) if you completed them and didn't receive the airdrop on the address you provided. Thanks.

Apologies for the delay replying to your question.
We extended the wallet testing period and Devs are adding extra functionalities to it, while increasing it's security.
The Fork, New wallet, Airdrops Platform and Release of Masternodes will all happen in under 2 months from now.

Thanks for your patience.

I invite you to join the Discord conversation: https://discord.gg/GgHJs8s

There is no minimum, you can stake any amount, the more you stake the more often you will receive the rewards.
Soon it will become Delegated PoS.

It is down at the moment, hopefully they will finish the change of their servers soon.

The Airdrop is LIVE until the end of 19th JAN UTC/GMT.

The issues with the wallet have already been reported to the Team and are known.
The Developers are working on a new wallet release which will fix those issues.
In the meanwhile you can find help and a temporary solution on the #wallet channel of our Discord chat: https://discord.gg/GgHJs8s
Thanks for your patience and support.

Thanks for asking, we have already received translations as bounties/proof-of-care before.
Let us know which languages would you like to translate to, we will let you know if we still don't have it and you could submit it on the proof-of-care airdrop bounty Wink
You would translate the white paper? It was never translated before
________


You need 40000 Castles to setup a Masternode, you can buy them on the exchanges.
Also available from the dev fund for a limited time only, see this tweet for details: https://twitter.com/Castle_CSTL/status/947708417514311680
________


Awesome just contact me or Lucas on Discord for more details if needed
________


Atomic Swaps would be used to change an amount of CSTL coins for an amount of another coin/token.
For example: Coins/Projects could use it to "sell" their coins/tokens to CSTL holders for a discounted price from their ICO price.
________


We are selling a few Masternodes from the dev fund very cheap to the community in order to fund the listing fee for coinexchange.io , we expect that to happen quite soon, we already sold 3 out of 6 Masternodes in only 2 days.
________


You can ask for help on the #wallet channel of Castle's discord. Please read previous messages as other people had the same issues before and the solution is most likely there already, if you don't find it let me know on Discord and I'll be happy to help
________


Airdrops are like giveaways, but in steroids, if giveaways still didn't go away, it is quite hard for airdrops to stop being popular (just my opinion, not financial advise)

Airdrops are needed by new projects to get out there and promote themselves. Castle makes it super easy for them to do Airdrops and we make the most of it with great marketing
________


You're in the right path.
Once the platform is live:
If you have Castle Coins, you will be able to request airdrops with basically 1 or 2 clicks, that easy!
________


Both.
Castle is an Airdrops Platform for other projects to use for the automation and promotion of their airdrops.
Castle is currently doing an Airdrop of Castle coins to celebrate the launch of the platform and of the first airdrop partnership.

News!: $RPT Real Property Token airdrop is now open until 10 JAN, even before the platform's release! You will find instructions and a form to complete on the #announcements channel of out Discord: https://discord.gg/GgHJs8s
________


Whenever you buy some or if you receive an airdrop.
For the CSTL Airdrop Platform Release Special airdrops, they will be delivered end of January to allow time for earning more up to 500 extra Castle coins by inviting your friends (with your referral link, which is on the form).
________


Thanks. Adding ERC20 functionality to our wallet may be an option to consider, but for now you can use any ERC20 wallet for receiving ERC20 token airdrops.
The Real Property Token ERC20 token airdrop just started and works like that.
See News! above
________

Thanks for asking, we have already received translations as bounties/proof-of-care before.
Let us know which languages would you like to translate to, we will let you know if we still don't have it and you could submit it on the proof-of-care airdrop bounty
You would translate the white paper? It was never translated before

Thanks for asking.
Castle holders will receive airdrops from other projects/coins who will be using the Castle Airdrops Platform, which will launch in some days.
It is a very easy way for projects to get more exposure, without all the work involved in processing airdrops manually.
Castle's Platform Automates the Airdrops.

The partner project doing the airdrop will have different options when it comes to the requirements to get the airdrop.

I hope this answer is helpful.
If you would like more detail, the white paper may help you understand better.

Thanks for pointing that out, it will be updated as that text is outdated.
There is a new airdrop going on that started under 2 days ago.
It is the airdrop to celebrate the "Castle Airdrops Automation Platform" Launch: http://goo.gl/7MM2eS

Thanks for the questions


Exactly 


Explorer: http://castleexplorer.tech/
Good Roadmap on White Paper: https://www.projectcastle.tech/White_Paper.pdf



Airdrops will be delivered end of January to allow time for earning more Castle coins by inviting your friends. Your referral link is on the airdrop form