My web vs. The web
The web has billions of pages. You'll see so few of them over your lifetime that the percentage is almost unmeasurable.
Your web, on the other hand, is well-traveled and familiar to you. It's the one you travel daily.
Facebook and sites like it are changing the world because they're becoming, for millions of people, "My web." Just as it's possible to do an entire day's work using nothing but email, it's now possible to live all day with your social network on Facebook. The new launch of open widgets makes that even more likely. I just discovered ztail, (which I haven't tested) which is an automatic process to let you create and then promote your auctions via your Facebook page.
It's not for every seller--it doesn't help you reach strangers, it doesn't help you teach people about who you are or what you do. But for those that are building their web around their social network, it's an inkling of what's to come. (hat tip to Fred for his insights on Facebook).