Why do I play this hand?

Party Poker No-Limit Hold'em, $ BB (10 handed)

Button ($92)
SB ($127.98)
BB ($37.50)
UTG ($75)
UTG+1 ($107.35)
UTG+2 ($233.65)
MP1 ($98.05)
MP2 ($109.72)
MP3 ($0.48)
Hero ($98.05)

Preflop: Hero is CO with , . SB posts a blind of $0.50.
UTG calls $1, 3 folds, MP2 calls $1, 1 fold, Hero calls $1, 1 fold, SB (poster) completes, BB checks.

Flop: ($5) , , (5 players)
SB checks, BB checks, UTG checks, MP2 bets $3, Hero ????

I hate being passive so calling seems wrong. Fold seems weak and raising seems too aggressive. What the normal play against the average opponent or one with no read.

I usually don't play AT, except if i open from LP, when ill raise with it.
If someone bets into 5 way pot, not being in last position I'd guess 80% of the time you're behind. I mean, I just don't think ppl play that much A9 and less. Maybe he played a suited Ace-rag, but he may have gotten 2 pair this way too. Raising and calling are possible, but if he has AJ (which I think he has) he will just call your raise and you'll know nothing. I don't think he has AQ or AK, but he'll prolly call with those as well. So raising here will be on pure bluff merits. If he doesn't fold you're out.
If you call you'll know that he was bluffing if he checks the turn and may proceed to win the pot so it seems to me that it's not worse than raising.

I'd fold though, even if he is bluffing, there is a good chance someone is slowplaying a set or AJ or whatever.

i think ATo is certainly playable here pf, especially if your opponents are weak. obviously not a super terrific hand, but playable.

on the flop, i would probably muck. yeah, it feels weak, but you are weak...an average player is not going to fold a better hand here, so basically you have to decide what are the chances your AT is good, and how much is it worth to you to find out. i don't think raising is a bad play, especially b/c you have position; just not something i'm fond of doing these days against "average" players w/out a big hand.

I played bodog for the first time last night, and at the $25 NL tables people were playing A5 A6 A7 A8 all the time. One guy dropped a bunch with A7 on a T73 flop. Good stuff. AT is playable there.

On party, despite the "fishy" reputation, A9 and lower are pretty rare (in my limited experience). AT is a limp with position, but an instyfold if anybody bets an A-high flop into you. What are you ahead of? A9 and KJ QJ JT J9. A9 is rare. And how many people bet second pair into a field of five? Why raise when four times out of five you are behind? Plus, one time out of ten he has 77 or AJ and you will lose a lot if a T hits.