Yep, all of that has happened in the past, along with some mistakes I've seen where members have entered someone else's btc or eth address when applying to a campaign.  This is why I generally don't tag many accounts anymore when it looks like two or more are linked.  I've had to remove quite a few negs because of this, and I'm not comfortable with that level of inaccuracy.

On the other hand, I do think often accounts can be linked by these sorts of transactions, but it's very difficult to tell the difference.  We all know damn well that bounty abuse happens and that a lot of bounty hunters think no one is paying attention and that they won't get caught trying to cheat.