as searching youtube can be slow (especially the first time when the user is not sure the plugin/search box is reacting properly :), for usability's sake, there should be either a "throbber" (like nautilus/epiphany) to indicate that a search is in progress, or a progressbar (pulsating?) indicating that a search is undergoing.

At the same time, it would instantly allow users to realize that when you scroll down the list, totem is actually expanding the search results.