I did this survey the other day that was giving a $5 bonus if you completed it. I didn’t qualify, so I just got the amount the HIT was for. The next day, I got an email saying I got the $5 bonus for completing the survey. A couple hours later, I got another email saying they realized it was a mistake, that I wasn’t supposed to get the bonus, and asked me to consider returning it. I don’t want bad karma, but I don’t see a way you can return a bonus? They technically did say, “And it is certainly fine if you don't, since it's our mistake”, so I guess that makes me feel a little better about keeping it, but I do know if it were me who made a mistake I would want someone to be kind enough to return it... :/