Just noticed that Facebook now has a marketplace, which is described this way:
Sell your stuff. List what you need. Browse friends' listings.
So, it's a Craigslist / Google Base competitor? But only within Facebook networks? That's what it sounds like to me anyway. You don't have to actually be a member of a network to view the listings, but you do have to at least choose a network to view listings from.
I suppose if your site can be marketed well in Craigslist or Google Base, then Facebook Marketplace is now yet another way for you to get the word out.