Most white hats are corporate parasites or lamers who are not smart enough to be black ones.
Often, but not always. You lose nothing by having a bounty on the test network, so people who really mean no harm can try stuff.
Bitcoin is in wild. It is looked over and over again by some really smart people. The Satoshi client is still standing. Is there a need for any more proof?
Yep, strongest reason why bitcoins are worth something right now.