Ask HN: what do you think are ebay's weaknesses?

I was chatting to a friend of mine about PG's "Ideas we'd like to fund" and we had an interesting debate about online auctions. At the moment, ebay has a near monopoly and my friend doesn't think this will change any time soon. I disagree. There are countless examples of start-ups disrupting existing monopolies.

Many people try to out-ebay ebay, and I think this is their mistake. There's not much wrong with ebay from a buyer's point of view. Yes it has it's flaws but not enough to convince buyers to leave en masse.

The seller's experience on the other hand is drastically different. The web is littered with complaints from sellers yet they continue to sell on ebay because that's where the buyers are. All the ebay competitors that have come and gone over the years have focused on tempting the seller away (usually with lower fees) but I think that's the wrong approach. Competitors should concentrate on winning over the buyers and the seller's will follow, but as I mentioned earlier, while there are no major issues with the buying experience, buyers will stick with ebay. I think this is what's behind ebay's recent spate of policy changes all designed to keep the buyer happy, regardless of the cost or inconvenience to the seller.

What are people's thoughts on this? Does ebay have an Achilles heel?