Re:Why no solid competitors? (Score 1)

Facebook is a potential competitor down the line. They definitely have a big enough userbase. They already have a Marketplace and they have a growing database of user's credit card numbers (from when users buy virtual gifts). They could charge auction fees, but seem pretty content getting most of their revenue from ads, so they could easily undercut ebay's costs by only charging their own bank fees for accepting credit cards.

Of course there are many things to consider when running an auction site, but a determined Facebook could get there after a few iterations.