The bitcoin blockchain is quite an interesting construct as it give us the possibility to send and receive money in a new way, well since 2009 at least. But the blockchain itself doesn't only consist of transactions which only say:
A sends X bitcoin to B
Using the Bitcoin Script which is also visible for anyone you can even send messages or hide information which can't be deleted. By bruteforcing your Bitcoin addresses you can also talk to people. It seems that WikiLeaks once tried to communicate with the publicy over Bitcoin addresses.
In prior there has been a post on 8chan which could have been posted by anyone.
Wiki Leaks decided to talk over their well-known own Bitcoin wallet and transfered money to themselves but hidding the message you have seen above:
"We're fine. 8chan post fake."
Comming from the address 13LBgLZ24X55mr8LqKddy9DusJtba17NCC you can see that the transaction https://blockchain.info/tx/fc722ce39094500690a4d4676fe475520d6a0af590336b73202010ca260bbd20 is sending money to the addresses including the messages. If you click on one of their addresses you can see that, afterwards the money has been sent further to their official WikiLeaks account.
Transaction: https://blockchain.info/tx/72162e9224dbadefb84834046ee8b4706af77f57fa4e8fd5aaf3255abf516807
I really love the idea that you can place messages just by using the right addresses. And I guess there are plenty of messages hidden within the Bitcoin Script of different transactions. I'll be posting about these secret messages later.