Some sellers have reported for some time that their profit margins on eBay are eroding. That's one factor that has prompted some of them to move some of their inventory to other marketplaces, such as Amazon.com, Overstock.com, and Google Base.See also my previous posts, "Google and eBay pursue sellers", "Disintermediation of eBay", and "eBay's search for sellers".
What's more, search giant Google is coming on strong. Its free Google Base listings service, coupled with a new payment system, threatens to undercut eBay by offering merchants a cheaper venue on which to sell.
Update: Reports leak out that eBay is considering teaming up with Microsoft or Yahoo against Google.
Update: Five months later, a BusinessWeek article reports the eBay "magic is gone ... Shoppers are simply not buying all the inventory anymore. Some items languish without a single bidder. Many shoppers opt for other sites including Amazon.com, use sophisticated search engines such as Google and Yahoo!, or head to store sites directly."
Update: Eighteen months later, Saul Hansell at the NYT reports that "sellers have become disenchanted with eBay" and "eBay is looking to reduce its listing fees and raise its final value fees ... [but] given the depth of the anger against the company, I wonder if that will be enough."