Recently bought a Droid 2, which was being sold with a $100 rebate. I fortunately photocopied the rebate form and my proof of purchase (POP) panel from my phone's box, then mailed the originals.
Today I got a notification that my rebate submission had been received, along with a link to check the status of the rebate. Ordinarily I would have assumed all was well, not followed the link, and waited patiently for my rebate. But, I clicked the link and found that they had rejected my submission (there was no mention of this rejection in the email notification - clearly they're hoping people won't notice they've been rejected), claiming the POP panel had not been included. Also, their system said my submitted rebate amount was only $50.
The website had no phone contact info, so I Googled "verizon rebate customer service phone" and found that it is 1-800-457-0864, and called. the guy I spoke with was very polite, but it took over ten minutes of combined talk and hold time to get things resolved (or theoretically so; it remains to be seen whether I'll actually receive the rebate).
He said they "did not receive" the POP panel, and that they had put me in the system for a different phone (thus the $50 rather than $100 rebate amount). I suspect the repeated holds he put me on may have included some time talking to a supervisor about why something that had once been stapled to my rebate form was now missing and the wrong phone type had been entered (it's very clearly printed on the rebate form) - maybe some pilferage at their processing center?
Anyway - my advice - keep copies of everything you send Verizon for a rebate, and check your rebate status carefully!