Originally Posted by DaNutsInYoEye
It may be your or my entire bankroll, but it is only a buy-in for him...
I would also think that someone with a set would try to extract as much money as possible, unless he thinks such an unorthodox play would entice a call. With your large re-raise pre-flop there are only a few hands I would put you on with AA or KK easily being the most likely. If he has a set there would no reason for him to be concerned about you having a potential 4-flush. The two others could be a concern, but he could have bet a lot less and still had it been enough to give improper odds.
If he has AA I can possibly understand a smooth call against one opponent, but I would think that after subsequent pre-flop action he would push when the action got back to him. At that point the pot was large enough that I think AA would just try to take it down then.
You didn't give any information about table dynamics or reads, but I could understand an EP call from him with a hand like AQs or possibly AJs. With enough money in the pot already the call of the re-raise would be fairly standard. With a hand like AQs a flop like that is hard to play from EP. Given the pre-flop action you can pretty much guarantee a raise from someone behind you and it's likely to be large enough that you won't be getting proper odds to call. You can either check-and-fold or push. If he has AXs I actually like the push. The pot is already 40BB and it would be nice to take it down right then. There is a good chance that going AI might get a hand like JJ or QQ to fold. A tight player with KK or AA might fold as well. Hell most people with AA or KK are really going to think before making this call, as this post is evidence of. Even if he does get a call he has plenty of outs to make his flush. If he does put you on a large PP, KK is more likely than AA since he has an A in his hand. This would give him an additional 3 outs. Even with a spade in your hand(which he doesn't know) he has 11 clean outs to beat you and with 2 cards to come he is only ~ 3:2 dog. With $1,000 already in the pot, if you call him he is risking $2,349 to win $3,372. He is basically even money in this situation. If you factor in the reasonable chance of you folding to his bet, he is probably actually +EV making this move.
Then again he could have been trying to get creative with a hand like 7,9 when called the first raise and then called the re-raise because he was then getting over 5:1. He then flops top two which is vulnerable to a possible flush or even an overpair so he is content to take down an already nice pot.