Talked to moneromooo on irc and this could pretty much work already. It would be cleaner if I'd make a new "tag" for the extra data but since tx_extra isn't used anyways it's the logical (aka easy) choice.

To insert data into it I "just" need to modify the wallet to send the proper RPC command. It should already be possible to construct a transaction with simplewallet in RPC mode using PARAMS="{\"extra\":\"hello world\"}" , which will be the next thing I test.

My seednode will be ready tomorrow. Any feedback, testing and help is hugely appreciated!

Sorry for triple-posting, it's not my fault that nobody recognizes the most revolutionary thing in the cryptoworld since Bitcoin.  

Yeah but it should be as decentralized as possible, is there a better way to securely store really valuable or important stuff than in the blockchain, where it lies forever, constantly verified by countless nodes...  

I am currently playing around with the idea of creating a blockchain to store data in it, be it messages or files or whatever. Just hugely increase the storage space for transaction data and add the data to the tx, right (OP_RETURN in Bitcoin and most Altcoins)?

Do you think it is worthwhile to seriously work on this? In my opinion there are many advantages, the biggest one: The data can not be censored, which is an interesting change from most of the Internet. Upload a file and it will be there forever!

I forked a Cryptonote coin to test if this is even possible, check it out here (Testnet): https://bitcointalk.org/index.php?topic=1835332.0

And why has noone tried this yet?

EXPERIMENTAL TEST RELEASE! MINED COINS ARE WORTHLESS! BLOCKCHAIN WILL BE RESET BEFORE LAUNCH!

Alright, I changed a few things (mined coins can be spent after three blocks, initial 150kb blocksize with 20% annual increase), sourcecode is here:
https://github.com/euleausberlin/infocoin

Compiling on *nix:

The resulting executables will land in /build/release/src and can be started with ./infocoind and ./simplewalletd .

Since there are no seednodes yet, you can either try to connect to my node:
(IP will change, not sure if reachable from outside, just a VM behind an ipv6 address, damn DSLite)[/s]

or you'll have to provide your own nodes or use the --testnet and --data-dir switch. More commands for the programs can be found here: http://forknote.net/documentation/daemon/

I will provide a seednode later if interest becomes apparent. Note that I wasn't able to test simplewallet functionality outside of testnet yet, always get an HTTP error 2 when trying. In Testnet it works fine, I guess simplewallet will work when the daemon is connected to a different daemon. Not sure about that though.

Two seednodes online, one in Germany, one in the US. Mining works fine!

Compiling on Windows is difficult and will be done later.

Note: I am a noob and things might be broken!  

Still need to find a way to add data. Trying to add data during the transfer via -p results in an error message about it wanting an encoded 64 char key, maybe that restriction can be changed or a similar function added.

Sorry for double posting.  

edit: Found https://getmonero.org/knowledge-base/developer-guides/wallet-rpc#transfer, this could totally work  

Zerocoin indeed looks interesting, it is possible to insert data into transactions aswell via OP_RETURN (max. 25 bytes). I will have a deeper look at it, the Lyra2 algo might be just the right choice to attract miners.

As for POS,  I never got the huge appeal, as I tend to not horde my coins. Properly implementing it would go way over my head currently anyways.

Thanks for the feedback, glad you like the idea.

Added a poll to learn more about the forum's opinion.

I'll clean up the code, change initial blocksize to 200kb and do a test release I guess.

I would really like to know your opinion on if I should go with a Cryptonote clone (data in TX_EXTRA) or a Bitcoin/Litecoin clone (data in OP_RETURN). I attempted to clone HODLcoin 1.0 (and a few others) but got stuck, documentation is really sparse when it comes to cloning Bitcoin Core based coins and I don't want to go with a four year old litecoin codebase. Will attempt it again if I am told that inserting data into TX_EXTRA on Cryptonote is a pain in the ass.  

Another big advantage of a Cryptonote clone would be the anonymity features.

I want to go with CPU-mining to provide some botnet hashing power btw. Since those are unlikely to disappear, they make the blockchain more secure even when "normal" miners have left, validating the stored information.

Infocoin aims to provide an uncensorable space for storage of information directly on the blockchain, a space to safely store messages, files, forums, anything.

For this purpose I cloned Cryptonote, increased TX_EXTRA_PADDING_MAX_COUNT from 255 to 102399, set the initial block size to 150KB and adjusted the blocksize growth to 20% per year. That means you can store up to 100KB per transaction, ofcourse you must pay a fee for which the optimal values will have to be found. Also the block reward is a thousandth of most Cryptonote coins (~700 initially). If these are sane values will have to be tested for sure, I'd also like to hear your input on these. Should feedback be positive I'll do an embarassing test release.

I am a noob when it comes to coding and forking coins, so I followed https://cryptonotestarter.org/inner.html for the most part, who have done outstanding work. Not sure if my changes will have the desired effect or break anything, so there will be a test release, to find out if the idea is even achievable.

Why did I go with Cryptonote? Well, because it's the only coin I was able to successfully fork so far. A Bitcoin clone might be way more suitable for this idea because of OP_RETURN seeing plenty of use already, so there are many ways to insert data into and retrieve data from the Blockchain already. TX_EXTRA doesn't see much use in Cryptonote coins so far and thus there is not much info to be found about it. I don't know how to insert data into the TX_EXTRA field in transactions, it is possible however (one likely needs a modified wallet to do this): http://monero.stackexchange.com/questions/1381/how-are-the-various-tx-extra-types-formats-used

If you are an experienced dev and like the idea, feel free to help or even take over. I just want to make the idea popular because the implications are pretty huge. It could be possible to e.g. make a forum that is impossible to censor, upload files, directly reward good posts. Astroturfing would be expensive as well, the fee should provide quality and security. So this is basically just a thread to see if the community likes the idea.

Also, yes, there have been a few Infocoins already, all seem dead and they didn't come close to the name anyways.

TO DO before release:
Find a way to insert data into transactions (tx_extra)
Explore other options besides Cryptonote
Seed node
Windows Wallet
GUI Wallet
Testing, testing, more testing

edit: TEST RELEASE in fifth post! https://bitcointalk.org/index.php?topic=1835332.msg18269690#msg18269690

edit 21st July: Network for testing is up and running.

PS: Why has noone tried this idea yet?  

Perfect illustration of the problem with Bitcoin: To transfer the funds he has to pay a 13.5% fee.

Not a typical usecase for sure, but it will become more and more common in the future if nothing is done.

Just think of the billion old XP and Win 7 computers in Asia, South America, Africa or Eastern Europe with non 64-bit capable CPUs. Why leave out 20% of potential users (estimation based on steam stats and http://gs.statcounter.com/os-version-market-share/windows/desktop/worldwide#monthly-201701-201701-bar )?

Just add a warning here to not encrypt the payload. 

When you deposit the coins it says something along the lines of "Make sure to send PayloadID, read more about PASL transactions at [forum link]", it does not say to send a non-encrypted payload, you must go to the forum to know that. Can't expect everyone to do that. Just add a warning, should ease the load on your support team as well.  

Glad to hear that my coins are safe.

I quote myself
Anyways, as long as this gets resolved I won't complain.

I understand that the chat is not for support, but it's a new coin and many users might lose their coins because they are unfamiliar with it, the exchange, the deposit process and because there are no clear warnings before depositing.

Adding "IMPORTANT: Do not encrypt PayloadID" should help avoid such issues.

Do not encrypt the payloadID!

https://www.cryptopia.co.nz/Forum/Thread/1016

I sent my coins with an encrypted payloadID, as it is the default option in the client. Cryptopia should really warn about this in the deposit box and not just some forum thread.  

Created a support ticket, let's see if they can help. They banned me from the chat after I respectfully complained there.

The problem is that at some point transactions under e.g. 10$ will not be possible due to high fees so everyone of those is likely to move. Anyways, interesting times.  

Your prediction of always increasing demand can only become true if the transactions stay cheap and fast. Otherwise volume and thus demand will imo decrease as people, especially those sending small amounts, will choose faster and cheaper alternatives.

Why should a coin die if a few miners keep mining it? Mining might even become profitable again.

I think both coins should and will coexist, hopefully in a peaceful manner.

Also just switch pools if you don't agree with them.

Releasing the "tools" gives devs a chance to close the vulnerabilities, otherwise they would stay open forever.

Apparently much more to come, will be interesting. 

I don't know, all this infighting lately surely seems weird to outsiders. Also the slow transaction-/high fee-problem must be addressed asap.

Otherwise things are looking great.

I have a good one. I mined 500,000 Quarkcoins over a period of a few months, back when it was  new and CPU only. The value plummeted, not unexpected due to the weird distribution scheme (block reward 2048 in the beginning, now 2).

After a few months of being around 40 satoshis the coin suddenly went up to ~300. I sold all, happy about the easy money. Two days later the price was at 25,000 satoshis, I could have made 175 BTC if I just had waited a bit. Never seen a pump like that again.

https://coinmarketcap.com/currencies/quark/

Without altcoins the network wouldn't be able to cope with the amount of transactions and the fees would be even higher.