I have mixed thoughts on that, but overall I would say it's fine. I mean, it's their web site and they can do what they want with it. Of course, the corollary is that Google is Larry and Sergey's search engine and they can choose not to list About.com if they want.
hmmm..ok... i agree its a valid sitemap and theres nothings wrong with it... it appears at rank 19 on google keyword for sitemap except the fact that it needs some more improvement to be more human readable than search engine bot readable. actually my goal in my experimental directory was to promote pages like sitemap, jobs, services, products, about, contacts etc thats why i accept deep linking for such pages like that. about.com must be a good role model for internet community.