Who are your Twitterfriends?
Most people are pretty honest in building their social network at sites like LinkedIn and Plaxo, connection to people with whom they have a real relationship. It also helps that if you want to connect with someone out of the blue, you often have to enter the person's email address.
Building your friendlist at microblogging site Twitter works differently though. On Twitter you send out your message to the world. Everytime you blurt something into the Twitterverse there's a good chance it gets picked up by someone you don't know. If they like your tweet, there's a good chance they'll start following you, and if you politely follow them back, you'll get into a new network, building your own. Networks on twitter can expand pretty fast to thousands of followers.
Stars of Le Web 2.0 often have massive lists of followers, like Barack Obama (555,878), iJustine (285,034) Guy Kawasaki (100,318), Robert Scoble (74,688). It's impossible to pay attention to everything your 'friends' say when you've got such a list to monitor. Chances are that you're barely able to follow about a 100 or 150 of them actively.
One of the nice tools that plug into Twitter is the Mailana social network analysis system, which taps into millions of messages, tweets and pulls up a nice graph of your Network. If your list of followers has grown too big to manage and you start to forget who your real friends are, maybe it's time to pull up a graph of your own to see who you've been interacting with. The image below is my Twittersphere, which you can explore here.