What always surprises me about lists like this is that there are people who follow thousands of others and they still get taken seriously.
My change of heart has come after 5 years of using Twitter. I could only follow 100 people well at first but somehow it crept up and up. I've had quite a few culls and now I'm at 1000 people I follow and whenever I go through the list I recognize almost every name. It's not quite a 4 minute mile but I've been able to get at least a feel for those 1000 folks and know they're ones I appreciate following.