Another site that is in the Quantcast top 100 is Answers.com.
It's interesting how they get their traffic:
As the search engine industry matures and expands in both user awareness and revenues, the core driver to this growth is the content that the various engines index in order to rank and then present to the user. Answers.com is continually adding and optimizing content to provide the "perfect page" to our loyal user base and to users finding our content through the search engines.
Basically, they get their traffic from SEO.
I am not sure what this means, though:
We are working on developing our business by increasing the volume of content we publish — specifically the type of material that enhances our advertising revenue stream — and by attracting dedicated, returning users for increased traffic.
Are they looking for commercial content?
My guess is yes. They have shopping.com integrated into reference pages. See right sidebar here. They also have an interesting integration of google ads. They place text links on reference pages which lead to a page full of cpc ads supplied by google.