Except at this point your parents are on Facebook. They were never on MySpace/Second Life/LiveJournal/GeoCities. While some of its value is "the cool place", it's also the place a lot of my family's social events (birthday parties, etc) are announced. If my 23 year old cousin switches to HotNewSocialSite, she'd still have to be on Facebook to find out about Granddad's 90th birthday get together simply because that's how the word gets out now, for better or worse.