Ebay has a market value of 12 Billion and quarterly sales of less than 20 million.
The recent stock price reflects an unreasonable view that this company will have no competition for at least the next 10 years. Same thing for most of the other Internet stocks. The big guys will not miss the opportunity to compete, and Ebay and other retailers/auction sites will probably not be around in the next 3-5 years. So, make it now - but don't be the last out the door.