[BugsBunny]

I think you're giving credit for too many outs here. I think the correct number is somewhere between 5 and 6. The backdoor I count as 1. The 7's are 3 (no more than that because one of the 7's is also part of the backdoor flush + redraw potential for a flush). Overcards in this case I wouldn't count too high. so maybe 2 outs for the overcards, 3 at best.

That gives 5 as a very conservative estimate and 7 as a high estimate. I think valuing the flush at .75 is too low. Flushes lose to other flushes rarely. Backdoor flushes, when they come in, lose to a higher backdoor flush even more rarely. That's because few people chase pure backdoor flushes in the first place.

The overcards are suspect, especially the 9 (98 is a very possible hand for someone to be playing) + add in the possibility of redraws.

I think folding this hand is CLEARLY wrong. You simply give up too much by folding these types of hands. However the comments about someone putting you on a flush draw and betting into you on the turn do have validity to them. Ultimately the decision on whether to raise or call comes down to what you think the chances of getting a free card are. The more people in the hand the less likely a free card is (for one thing the more people the more likely the turn will hit someone).

So ultimately I still think it's a close decision, dependent on:
1) Chances of being 3 bet on the flop
2) Chances of getting a free card

Note that if the players in the game like to be "tricky" (c/r at the wrong time) your chances are better, since now - even if they have a hand - they'll call the flop and check the turn planning to "trap" you with their ultra-tricky c/r move.

So the real question is how to play against mostly unknowns (often the case, especially when multi-tabling). With the aggression levels (and better post-flop play) at something like 10/20 I suspect a flat call is probably correct in the majority of cases. At 5/10 (where this hand was played) the players tend to be more passive and worse postflop (as a whole, there are exceptions) so a raise may be more effective. But I think it's close.