If you ask investors, nothing. eBay has increased their profits an average 89% year-over-year for the last 10 years, making them the best performing company in the US right now (second place goes to Sealed Air, maker of the world's only additive packing material, Bubble Wrap, way back at 55%), perhaps the best performing company anywhere, ever.
But if you ask the customers, you get a very different answers. To hear them talk, the site is nothing but scammers stealing merchandise and credit-card numbers, thieves selling stolen goods, and retailers dumping seconds and over-runs. The Pierre and Pam Omidyar's original vision of a consumer-to-consumer marketplace for quality used goods seems like a fading memory.
Actually, every consumer-to-consumer (C2C) site has this problem: since the site owners have no control over either side of the transaction, and the basic business model necessarily requires many more transactions than is possible to monitor. A popular C2C website is just blood in the water for every scumball from Mountain View to Mumbai.
I used to run a dating site and it was the same thing: cam-girls (women advertising online strip-shows), credit-card scammers, and other assorted riff-raff made life hell for my customer-service people.
So, can C2C be saved? I hope so, but I'm skeptical. The only possibility I see is if the social-networking sites make it possible to establish what are called "chains-of-trust".
You've heard of six degrees of separation, the idea that every person on Earth is joined by a chain of friend and acquaintances no more than (or "on average", depending on who you talk to) six people long. If Facebook allowed you to know that, oh, Bob went to college with Giles, who used to work with Cynthia, who is in a scrapbooking club with Myron, who's your brother's chiropodist, and each person in that chain vouched for the next, you'd be a lot more inclined to accept Bob's check for that Stairmaster you're using now as a clothesrack.
The only company really doing chains-of-trust is LinkedIn, but unfortunately, that's about all LinkedIn is doing, that and doing résumé searches for industrious employment recruiters. eBay is probably too stodgy to do it, and Facebook itself is too busy.
Maybe someday, I'll get enthusiastic and write a Facebook app for it.