Not some subtle but plain simple. Like using personal email to register on forums and promote SR and recruit people.
Using stackoverflow with personal email, again... Yes they are not some solid evidences, but made the FBIs life, to get the guy, much easier. You might say that it's easy for me to point out those mistakes but they are so basic and it's not that he was running some Nigerian type of scam, he must have been way more careful.
Or keep messages about the 'murder-for-hire'. Yeah it's rather obvious that no one got hired but good luck explaining this negotiation tactics to the judge. Plus he mentions $80k for other 'murder-for-hire'. I'm really curious how the thing with this 'murder' will end up. I mean he could have just simply deleted them just in case. It's not FB that it would stay forever...