Buy.com sent me an email saying the rebate was a mistake, I emailed them back and they said talk to rebate-zone (www was worthless, but phone was free and not a long delay for a person).
CSR took my name etc., read the same oops some other store posted the rebate showing buy.com without authorization.
I told her I got my rebate from a link on the lexar site, not a competitors, and we went back and forth a bit.
CSR then said, send in the rebate I have ($40) and it will be escalated to a supervisor and processed.
She didn't really say, yes I will get it, just kept repeating supervisor and processed. I "think" that means that if I filled it out completely etc etc. I get the $40, but enough doubt and my wife saying WTF did you buy that for (old 512MB is fine for her palm she says), so I emailed buy.com about returning it (what their original email suggested) and I plan to just do whichever seemed the least troublesome.