I've done that. I hold the trademarks ANIMATS (supplemental register), SITETRUTH, and DOWNSIDE. I have the domains "animats.com", "sitetruth.com", and "downside.com". Those were all obtained simply by filing directly with the USPTO. Unless you're in a crowded area of the namespace, trademarks aren't hard.

Owning a trademark gives you strong rights in domain name disputes. This is effective even if there's someone else who's a big name in a different business area. See ICANN's UDRP.