The rules for most PIFs (like Noob PIF) specifically tell participants to give trader feedback. Like you say, it is a trade, just spread out over a larger group. I tend to give reputation freely, so if I got a nice selection of sticks, I'll bump.
My general rule is that if someone commits to send me cigars (whether a one-on-one trade, or a PIF, or a MAW) and they follow through, I always give trader feedback and often a bump in rep. I don't give trader feedback for bombs, but I always give a bump in rep.
BlackIrish