Are carousels effective?

Go to just about any eCommerce site and the homepage is nearly guaranteed to feature a carousel - an auto-rotating panel, usually with some sort of small navigation, usually highlighting new product releases, sales or offers.

Are there any studies out there that look into how effective carousels actually are in terms of conversions and as compared against other ways of displaying similar information? I have a hypothesis that they might be something of a UI cliche, partially supported by looking at click data from some of our own sites.