Today was the kickoff of custom URLs on Facebook and perhaps the advent of an interesting bout of digital identity crisis for some. For most things online, I’ve always stuck with the handle christmasgorilla—it’s a useful mnemonic for my full name.

But when I went to went to grab my Facebook name, I decided to go against the history of the handle and choose my family name: facebook.com/muscarella. Now I’ll admit that part of that was based on a recent googling showing that I was slipping in the ratings and some sort of need to own my family name space. But it also brought up an interesting thing about digital identity.

Facebook has always shown the full name of it’s users, which has always given status updates on the site a strange kind of gravitas over things like AOL chatrooms or Twitter. Further, the nodes of people in Facebook are usually those that know each other in real life and may be quite unfamiliar with the full extent of each other’s online identities (IM handles, email, twitter, etc). And it seems like I’m not alone in my choice. Most other people I know with extensive online profiles have opted for some variation of their proper name as their Facebook ID.

If Facebook can actually succeed at smudging the line between online identity (Facebook Connect), networks of friends, and other web services, they will have created the worldwide address book of the future. I used to be somewhat skeptical of that until I witnessed my own choices this morning. And that I was able to call someone a few weekends ago from Facebook when I didn’t have their phone number.