The forum experts stated really well what are the possibilities of generating the same address with someone else. You can try your luck on
this thread, though.
I would like you to check
that too.
(Made by me :p)Otherwise, taking someone else's funds has a simple definition: theft.
Many things have a probability, but it doesn't mean they will also ever happen/exist. Generating two identical privkeys is one of them.
It hasn't ever happened, and it won't, but even if someone stole the funds, what could the victim do? It isn't an actual theft. He didn't broke into his house or hacked his computer. I think that the "thief" can keep the funds legally.