How do I prod my Droid 2 into resync'ing Facebook profile pictures?
From what I understand, Contacts is actually fairly decoupled from Facebook because Google doesn't like their API and Facebook doesn't want to let their users export data.  I believe this means that if you remove your Facebook account from the phone, those photos will disappear from the contacts.  Then you can re-add the account to get them back.

Unfortunately the contacts are not likely to relink automatically after that, and you'd have to do it manually every time.  I don't know of a better way.