Most of you guys will go with the known trusted users but let me get you a hidden gem. A newbie who made only 5 posts until now but got +7 green under his profile for the very one reason which is being honest and you can see that theymos mentioned the word honest as well.
In this situation it turned out we had
two dummies: owlgames sent the BTC incorrectly to the forum, and then yesterday
I sent his refund to the wrong address.

I'd been referring to my previous notes on how to do the refund correctly, and I sent the BTC to the
last person who overpaid, since their address was still in my notes and I forgot to change it this time. (Now I've rewritten these notes to remove addresses...)
I thought there was little chance of getting the BTC back, since the last person who overpaid looked fairly anonymous, and in any case they were probably using an exchange address or something. So this morning I refunded owlgames properly in a second transaction, and I expected to just eat the cost. But surprisingly, the person who got the random $1000 I accidentally sent,
EZ0010, returned the BTC ~immediately. Thanks to him!
The lessons:
- There are good, honest people in the world.