Google is gathering the e-commerce pieces together. Today they put up Google Payments so you can buy stuff and pay through Google. It's visible for certain items on base.google.com - like this: Wanna buy a rock?
Combine base and payment and you get an odd form of Craigslist meets PayPal, with Amazon/Ebay Marketplace thrown in.
Is it any good? Let's wait to see what Paul Kedrosky says. But obviously it's early.
Google is also a bit like Microsoft used to be - their stuff doesn't need to be that good for millions of people to try it. And it's likely that they will eventually subsume the dominant paradigm because they have the most traffic that is searching for something to purchase.
Update: Go here to get on the Google Payments seller waiting list.