FB URL's used to be a right old hodge-podge and this is much better for branding, business cards, and generally professionalises your presence. Seriously, if you've been living under a stone and haven’t yet grabbed your custom URL, head to Facebook.com/Username and get to it, stat!.
Now, if you’re an admin for a Fan Page, you can grab custom URL’s for those too. Head to Facebook.com/Username as before and follow the "set a username for your pages" link, as per Facebook.com/doyoukasasa for one of our clients, etc. Here you can check no ones run off with your brand name already and grab those keyword friendly URL's. I thought this was a given, but, turns out a lot of folks don't know about the Fan Page bit. Only one small caviet, to make sure you're serious I guess, is the group MUST have over 100 members. Don't miss out on this, theres only 1 chance to grab the name your after.