Well I currently have one on one of my characters, though its a pitiful 15 million credit one. Usually my Kiretsu has a 50 million credit bounty or higher. There was a period of one month where I had a 400 million credit bounty, though that was an incredibly OORP bounty that the person later took down. Never had anyone collect a bounty on my Kiretsu yet. I make killing me very difficult.