You probably want the ad stats: https://bitcointalk.org/adrotate.php?adstats which are more helpful than the number of registered accounts.

There should be a lot of software to recover deleted files. Just Google around for them.

Oh I see. This way it pretty much never risks users accounts even if you are hacked. It would require a malicious browser extension.

How exactly does a browser extension with with this? I thought it was supposed to just be a website.

Bitcoin core doesn't necessarily receive blocks in order and it writes them to the disk in the order it receives them. This is probably the problem you are having.

Oh, I'm running my own compiled version of the master branch. 0.12.1 also works on it.

I don't know why the ppa doesn't have it though.

What do you mean it isn't supported? I have bitcoin core working perfectly fine on Ubuntu 15.10.

Possibly. You should make a backup anyways. To backup, just make a copy of the wallet file and put it in a safe location.

Theoretically, yes, however it would require many things to go wrong. First, you would have to allow the infected firmware to be installed. Secondly, you would have to disable the check for a properly signed firmware or the developers of trezor would have to be hacked. Only then could it work.

Yep. That's exactly what it is for.

Holy crap that is super old and outdated software. It is expected that it shouldn't be able to connect because Bitcoin's method of discovering peers has changed since 0.3.19.

Download and install Bitcoin Core 0.12.1 from https://bitcoin.org/en/download. Bitcoin Core *may* be able to read the wallet file (I think it should since not too much has changed in the wallet file). You probably have to run Bitcoin Core with the -upgradewallet option.

Bitcoin transactions are made of inputs and outputs. The inputs spend previous outputs. Your transaction spends from a large number of outputs, thus it has a large number of inputs. Validating a transaction with many inputs can be resource expensive.

Blockchain.info's node has a policy of rejecting any transaction with over 250 inputs probably to reduce resource use on their node. However, if a block includes such a transaction, then they will accept the transaction. This is what happened with your transaction because it had too many inputs.

10-16 connections is not low. There is nothing wrong with your node. You can only have a maximum of 8 outgoing connections, the rest of the connections can only happen if people want to connect to you, and clearly they are.

Your connection count will increase as your node stays online longer. If you take it on and off every day, then your connection count is going to be lower than if you leave it on.

Not that many, and certainly very few that understand this sort of crypto. Of the Core Devs who are here, we only have gmaxwell occasionally and maybe luke-jr. Since you are asking about the schnorr signatures, I think it would be best to ask on the #bitcoin-dev irc channel where there actually is discussion, or at the very least, paid attention to by developers, unlike this forum.

Edit: for stuff on schnorr sigs, I don't think anything "official" has been done yet, it's all experimental. You may want to take a look through the changes here: https://github.com/bitcoin-core/secp256k1/pull/212 which introduced schnorr sigs to libsecp256k1.

MultiBit HD is not compatible with Multibit classic. It also can't import keys. Rather, your friend should download MultiBit classic from https://multibit.org/releases.html. Then he should load his wallets and send all of his Bitcoin to addresses in his new MultiBit HD wallet.

It should be fine to ask them here, but given the lack of Bitcoin developers on this forum, you probably won't get any decent answers. Try asking on the bitcoin-dev mailing list or on the #bitcoin-dev irc channel.

Armory wallet files are .wallet

A paper backup is supposed to be printed, not saved somewhere on the computer. The file extension is then whatever you saved that backup as. Also, paper backups aren't encrypted.

Then try the password and see if it works.

If you want to brute force it, check out this software: https://github.com/gurnec/btcrecover

You can brute force it but it is going to take you a very long time. Without any idea of what your password is, you pretty much have no chance of guessing the password. Even though 0.223 seconds seems like its really fast, in computer terms, that is a ridiculously huge amount of time, especially when you want to brute force something in as little time as possible.

Not necessarily. No one knows what the price will be after the halving. Anyone saying that the price will be something is just speculating. It is impossible to know the future and Bitcoin's price is not guaranteed to go up nor go down after the halving. You can buy and sell whenever you feel comfortable doing so.