As joblessjunkie mentioned, novelty is a huge draw. I've seen ads on Facebook, Yahoo and MSM sites (probably delivered by ad networks) that feature eye-catching faces with some ridiculous or unusual element (long beards, tattoos, elongated teeth etc.), but are advertising something that's pretty mundane (loans, online education, etc.). They are much more noticeable than ads that use standard art or photographs.

Judging by the fact that the advertisers are still using weird face ads, the CTRs must be superior ... but the interesting questions would be around the type of customer or conversion rates.