US Airways Dividend Miles (Pre-FlightFund Merger) - "Free" Silver Preferred Status w/ BA?

My roommate in Virginia just got enrolled in Silver Preferred on US Airways. What has me curious is that he's never flown on them--all he did was fly to London and back from D.C. this summer. Has anyone else heard of this?

If US sent him a complimentary Silver membership, it's likely due to his living in DC and perhaps them having a travel profile on him of some type (airlines and credit cards sell this info).

London & back is enough to qualify for Silver under a challange. Maybe he signed up for the Dividend Miles program and the challange as well?

That was my thought as well. LGW-PHL is about 3500 miles which alone is enough to qualify on a r/t ticket.

I thought all those things, but the title of this topic is "Free" Silver Preferred Status w/ BA", plus Joshua said his friend never flew US. My assumption was that his friend flew BA to London (hence the "BA" in the title) and still got a comp'd membership from US.