I'm kinda a Bitcoin Noob, however, I hope years from now people will still see 2014 as an "early adopter" phase.
Almost lost about $35 USD worth in a password protected Multibit wallet. Finally realized I mistakenly had my cap lock key on when I originally typed in my password.
Then, I'm always concerned about losing my 2-factor Authentication phone for an anonymous web wallet only accessed thu Tor, therefore, I try not to keep much online.
So thus far, none for me (knock on wood), but I can easily see how BTC can eventually be carelessly lost in cyber space.