Ebay- Source of Income?

In a question posted to the Ebay site, a seller asked if she had to pay taxes on her income from the sales she made. Ebay "The World's Online Marketplace" is the home of more than 135 million buyers and sellers and rakes in $34 billion from sales made last year. The government does have a guideline for paying taxes from these types of activities. For instance, in the state of West Virginia an individual is required to pay income tax on any winnings from the lottery that exceed $1200. In Las Vegas prostituion is legal as long as they pay taxes on their profits. So, should people that buy and sell on Ebay be required to pay income tax on their sales? Is enough money made from these sales to even tax somebody? And, what economic impact would this have on the Ebay organization?