Many have questioned AT&T's policy of charging top dollar for MicroCells to offset their generally lousy cellphone coverage, but it appears as though they may finally have seen the error of their ways. So far we have been unable to figure out exactly what criteria they are using, but they seem to be selectively handing out vouchers to pick up a complimentary MicroCell if you're a "loyal customer".
The tipster who submitted the lead to Engadget claims he only pays about $180 per month for his family plan, and has never complained about the service in the past. As far as he can tell, he was picked at random. Perhaps it's the fact that he hasn't complained that earned him the title "loyal", but your guess is as good as mine.
If you've been on the fence over the whole Microcell issue you might want to try and hold off a few more weeks until we know more. You might just have a free coupon in the mail.