A truly brilliant new use for captchas. It's the best of mechanical turk (where small amounts of human labor are aggregated up to produce large amounts of useful work) and Google suggestions (where information is added simply by what people do on a regular basis). It's server-side, and I can't decide whether that will spur adoption or hinder it. My guess is it will hinder early adoption (because you require large, conservative organizations to do something new) and ultimately increase penetration (because once they do, you have 100% penetration among those companies' customers).

--Ari