I will judge a lens based on its individual quality. Similiar to a wikipedia subpage, blogger/wordpress blog...
http://www.squidoo.com/ Example page - http://www.squidoo.com/organicotton Its almost like wikipedia.
Occassionally. The site is pretty good at spotting unlicenced duplicate content and dealing with it (you can only put in Wikipedia text with the wiki module, as it adds on relative footers). They're used more for people, rather than search engines. My lens - A Beginner's Guide To Retro Games - is ranking pretty well
Seems like they are somewhat of a giant advertising page. You sign up for a particular keyword and can put links and some RSS-type content. I wonder if a lens provides information that would be useful for someone who comes to my directory to view. They just seem like so much less than a site as they have very little unique content. Those of you who would accept a lens, would you also accept someone's Digg/Stumble/Reddit, etc account page? Seems like they are quite similar.