Branding, perhaps, but I don't think you could say "at it's best" since a major sacrifice is consistency; something a lot of brands feel is very important.
Oliver Henniges pointed out the possibility of WebmasterWorld.Com vs WebMasterWorld.com vs Www.WebmasterWorld.com and all the other variations. It's impossible that you would arrive at any level of consistency across multiple users with this approach, except with lengthy rules regarding casing of subdomains, second level domains, acronyms, etc.
Personally, I'd prefer users to know instantly that ExampleBrand is a brand name and www.examplebrand.com is a URL. I think this outweighs the potentially for increased visual appeal. And hey, we've got anchor text in any case, so that browsing the web doesn't involve a lot of reading of URLs.
[edited by: Receptional_Andy at 2:14 pm (utc) on May 18, 2008]