GlimmerBlocker has a better method: it is a general ad-blocker which can block http requests to Facebook from 3rd party sites. See the Facebook filter on http://glimmerblocker.org/wiki/Filters
GB can do more than just blocking requests: it can modify both the requests and responses.
My buddy Justin wrote this last night: simple menubarlet to redirect facebook.com requests to a local webserver when you want. Using this and a sensible privacy setting ought to make Facebook much more amenable to privacy types.