[rb2k_]

Usually as a starting point for a crawler when checking statistics about the web.

Crawling is much faster if you don't have to "spider" all the links and check if you've already visited them or not.

With a big enough list, you can just iterate over those domains. (average number of links on a website, how often does javascript framework x vs y get used, how many sites have an HTML5 doctype yet, ...)