I form first impressions very fast, and since I make a lot of friends through Twitter I've figured out some different ways of evaluating their profile to make some generalizations about who they talk to, how engaged they are with people, and what they're interested in. It's much faster to read someone's last 100 tweets than to read their last 10 blog posts. One thing I look at is the ratio of followers to following. The reason is that I've discovered there is a balance between the two - if someone is following too many people (far more than are following them) then they are likely a spammer. Twitter controls for this by making it so that you can't follow more than 2000 people until you have at least 1800 people following you. On the other end of the spectrum are those who are followed by many many people but make themselves seem inaccessible by following back only a tiny percentage.