oh I'm sure that massive amounts of fraud happen at paypal and others...  but in this case I wouldn't say "extremely stupid behavior" ...

Mybitcoin :  $1,300,000   --- this wasn't "stupid"  this was outright madness....

Polish Exchange : $255,000 -- okay this was stupid... dude deleted his exchange's wallet with 17,000 coins in it...

Dudes Desktop wallet stolen : $375,000 --- okay this was stupid as well,  using a compromised windows box as his sole wallet.

Goxed : $10,350 plus surrounding problems (this figure is most likely on the low end, but i'll use it).  --- this wasn't stupid as well,  this was a mixture of growing pains (from hobby to real business) mixed with some serious hacking.

I agree with you 50% of it was stupid...  the other 50% .. that's more like criminal behavior mixed with simple growing pains..