I have recently encountered a very clear case of group bounty gaming.
SO post in question: Triggering event manually in JS Helper CakePHP
The original posted of the post started the question, did not get a single response for more than 2 weeks, hence offered a +50 bounty, which I believe is legitimate up till this point.
I saw the bounty, answered it on the same day of the bounty. No response from the original poster for 5 days since the answer. I posted a comment 2 days before the bounty ends just to see if he got what he asked answered. No reply from him.
Today the bounty ended. Just mere hours before the bounty ended, a new user popped up with an answer that is too similar to mine, with mere changes in Class and some variable names. Within minutes, his answer got accepted.
Did some investigation myself and found out that they were friends on Facebook.
I believe it wasn't intended to be a foul play at the start, but once the original poster got his answer, he felt reluctant to give away his +50 reps to someone (in this case, me) who has actually answered his question and got his friend to quickly post a plagiarized answer and immediately marked as resolved.
I flagged it, but I wonder are there anything moderators can do about it besides simply acknowledging it?