Individual hobby thieves and hackers surely do mistakes and get caught from time to time but this is virtually harmless compared to organized crime. Thats the biggest problem with Bitcoin today. There seems to be zero interest by law enforcement/governments to go after that kind of criminals ...it looks like they waiting for a good timing to use all these scandals to say "See, we told you but you wouldnt listen, banks are safe, Bitcoin is not".

As people pointed out before its also the sheer stupidity of some users, the greed for fast profit etc. that makes alot of people lose money. Having said that, no exchange can guarantee you some safety these days and if something gets too big, better play safe before you lose it all.

Personally I believe the "hacks" including Mt.Gox were just a scam .. .in a weird way they are protected by law... thats the pros and contras.