Companies may try to capture their trademarks anywhere in URLs.
When Facebook announced that it was letting users reserve vanity URLs, the company put in place trademark protection measures. Twitter also has rules governing the use of usernames, which are found in Twitter URLs as Twitter.com/username.
It makes sense to protect both companies and individuals from people impersonating them on social networks. But it also sets a worrisome precedent that other social networks — and even regular web sites — will be subject to trademark holders claiming rights to disallow trademarks anywhere in URLs. For example, if I had a page at DomainNameWire.com/Coca-Cola.html, the company may ask that I take it down.
If this sounds far-fetched, just ask anyone who has received a cease and desist because of a keyword meta tag on their web site (I have seen those) or a company name being mentioned somewhere on a web page (I have received one of these).
Trademarks should be protected at two domain levels only: the top level (e.g. .com) and second level (e.g. company.tld). Domain owners should be allowed to use a company or trademark name in a subdomain (a.k.a. third level domain) as well as any directory. I worry that the policies of Facebook and Twitter may get trademark lawyers to start expanding that definition.