These Facebook Like buttons appear at the top of the page, directly under the listing title. The buttons do not appear in all categories yet, but are starting to show up on a few of my own listings--mostly those with free shipping.
I had heard a little bit about it at the eBay convention in Las Vegas last week--eBay told us that "We're actively working on putting more "Like" buttons on the site."
I, for one, "Like" it.
