When is passive play right?

First post, long time reader (thanks to all who do post).

I'm a 15.5/7.5/3.8 player over the last ~20k hands, so don't think aggression is a problem for me. Preflop is obviously weak, but what do think about the line from the flop on? I've only seen villain for one rotation; no reads.

Party Poker 2/4 Hold'em (9 handed) FTR converter on zerodivide.cx

Preflop: Hero is SB with A[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/spade.gif[/img].
<font color="#666666">4 folds</font>, MP3 calls, <font color="#666666">2 folds</font>, Hero completes, BB checks.

Meh. Whatever.

Flop: (3 SB) T[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/club.gif[/img], 8[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, BB checks, <font color="#CC3333">MP3 bets</font>, Hero calls, BB folds.

There's no way I'm folding here, but a bet doesn't seem right either. If I bet and he has it, I lose more money than just calling. If I bet and he doesn't have it, he folds and I make nothing.

Turn: (2.50 BB) 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP3 bets</font>, Hero calls.

River: (4.50 BB) Q[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP3 bets</font>, Hero calls.

Final Pot: 6.50 BB