What you are doing is copying the reciept and sending in the rebates that you shouldn't be getting. Because it goes through the mail, its mail fraud.
You've "gotissues" man...
And why shouldn't you get the rebates?
Most large electronics / office supply stores have price match policies. You are allowed to price match for 7, 14 or 30 days. You buy and item, later you find a lower price, you go back and ask for the difference back. You use your receipt to do that. Are you saying if I find a lower price (which I have done many, many times), and I have already sent in the rebates, I am all of a sudden a criminal? I cannot imagine 20 days later finding a lower price (after sending in the rebates) and saying to myself "I better not go to OD and get my pricematch, I'll be committing mail fraud!"
What if you pricematch up front when it is purchased then send in the rebates? Is that mail fraud? What is the difference in your scenario?
As someone has already mentioned, unless the rebate forms terms specifically prohibit receiving the rebate if a product is pricematched, then there is absolutely nothing wrong with it - OD's forms do not. Even if it did have the BB statement "you are not eligible for this rebate if you pricematch" just sending in the form would not constitute mail fraud, only a rebate denial.