I see lots of posts about this. Frankly, I'm tired of always typing in the replies to people, so I'm going to do it here, and that way, I can simply link them to the post and they can read it. IMHO this should really be made into a sticky, because not only is it a common question/concern, it's good info that will help assuage people's fears about PM's and rebates. Next time someone asks "will the MIR be denied since I got the PM?", just post a link to this thread.
A lot of people don't know this, so here's how rebates work; this applies to either store and/or manufacturer rebates:
Company X advertises a product with a mail-in rebate. Company X contracts with an RFC to fulfill said rebates. Company X pays the RFC the amount they *think* they will sell, and the RFC is then in charge of fulfilling said rebates. (For example, if Company X expects to sell 1,000 items and there's a $10 rebate, they will pay 1,000 X $10, or $10,000, to the RFC, plus a cost of X per rebate, usually around $5, so another $5,000 for a total of $15,000.) Now, this is where it gets tricky, but stick with me: the RFC is paid per expected number of rebates to be fulfilled, but not only that, any rebate that goes unfulfilled (either by the total rebates redeemed is less than what company X expected, or by the RFC rejecting rebates for whatever reason), the RFC keeps the amount left over that was paid by company X to begin with to fulfill the rebates. In effect, they double-dip, which is where their real profit comes in. It's estimated that only 60%, at most, of consumers actually send in rebates. Of those 60%, at least 10% are rejected by the RFC for various reasons: not including a clear receipt showing the item purchased, not having the rebate postmarked by the specified date, not including required items like the UPC, etc. Some of the more "notorious" RFCs will actually deny 20% of MIRs out of hand, for no reason whatsoever, and wait for the customer to contest it; if they don't, they win (they keep the money), and if the customer does, the RFC pays, which isn't a loss since they expected to pay already. For them, it's win-win, since they get paid either way. They just get paid more if the customer doesn't contest it.
What happens when more rebates are sent in than company X expected? The RFC goes back to company X with their documentation, and gets paid the additional cost. The RFC will basically say "you told us 10,000 MIRs would come in, we got 15,000 already, and we're expecting another 5,000 as well", so company X will pay out to cover those actual *and* expected MIRs. There's also, usually, an agreement that company X will have to pay a penalty for that to the RFC (which means more profit to the RFC.) This is also why sometimes it takes longer to get a MIR fulfilled, since the RFC goes back to company X to get more funds to pay the rebates, and won't fulfill the MIR amount until company X pays the RFC.
The MIR game is actually quite profitable for the RFCs, and there's a lot of fly-by-night RFCs (yes, I know some of you will mention the Buy.com MIR fiasco, which is a prime example.) There's also several very reputable RFCs, who fulfill on time and even very quickly. It's not hard to figure out who they are (the address is the giveaway), and people here on FW have a list of them somewhere (but I can't remember where.) Some companies actually solicit bids from RFCs, where they try to get the lowest cost (per MIR), while others only deal with one RFC (OD is a prime example, and only deals with the RFC in Young America, who's name escapes me.) Typically, the more reputable RFCs charge more to company X, and the fly-by-night ones charge less. That's where the gamble (for both company X and you, the consumer) come in.
Capiche? Hope this helps you understand the MIR game a little better. In closing, here's my tips for making sure you actually get your MIR:
Since I first started tracking MIRs (using Rebate!Rebate!) on 05/19/2003, I've spent $11,001.21 on items, another $105.61 on postage, and gotten back $7,094.80 in rebates. Which means I bought $11k worth of stuff for $4,012.02. Not bad at all. Of course, not as GREAT as I'd like, but still, an overall 64.491% discount over 157 purchases covering 4 years isn't bad at all.