I bought a laptop from CircuitCity last year, that had a laptop rebate, a bundle rebate, a printer rebate, and a router rebate. I think I got all of them.
I really tested the waters two months ago, I ordered $750 worth of computer parts with $350 worth of rebates. So far, I've recieved my CoolerMaster rebates (2), my BFG rebate, and just recently my TrendNet rebate. I still haven't recieved my Xion rebate, my EVGA rebate, my ThermalTake rebate, my Foxconn rebate, and most importantly, my $200 rebate from HP for their infamous DDR2 RAM. That last one disturbs me, because many people reported recieving their rebates in a short period of time, sooner than two months.
Despite that, I ordered more parts with rebates just recently. A CM RC-330 case, some HyperTX2 CPU coolers, and a ThermalTake Xaser V with an $80 rebate, a 3DFusion (BFG, I think) video card, and a VisionTek X1950Pro from CC. Haven't sent the last batch out yet.
Always photocopy everything. Non-scam rebate houses will allow you to re-submit/re-verify your rebates if you have documentation. Scam rebate houses will say things like "no re-submissions allowed", etc. Avoid them like the plague. Rebates411 isn't too swift either.