Stealing is illegal act, but to report it to police you need to be legal in country you live. Yesterday I saw news about one guy who got 6 months jail for bitcoin ponzi scheme, that was in US. I don't think every government will proces this things.
Bitcoin still need to get laws that determine borders of legal and illegal, Russian's talked about banning bitcoins and I doubt someone can report there stealing of bitcoins.
Defenitly thiefs and scammers are using this 'no laws' situation, they are aware that even if they get caught nothing will happen. Cause of this people are still afraid to invest in bitcoins.
There's a big difference in "randomly generated" and deception.
The usual thing is that, if you generate an address, it's yours. Do whatever you want with it including taking the balance if it has a balance.
Deception, on the other hand, is illegal.
For me, if ever I generated an address with a balance, I'd post a signed message that bitcoin, or the underlying hashing algorithms that generate BTC addresses, is broken. Hashing algorithms aren't supposed to have any collisions.