There is some debate about the worth of followers, friends and subscribers. (Check out: What Are A Million Social-Media Followers, Friends Or Subscribers Worth?.)
I know there are some on Twitter who try to score as many followers as they can, as quickly as they can.
I generally find the content of those people's feed to be uninteresting and unhelpful. I generally don't follow them.
I think quality is more important than quantity.
By quality, I mean people who actually read your posts and people responding to those posts, either engaging in an online conversation with you or by retweeting your comment.
I can tell that more people are clicking on my links in April 2009 than were clicking onto them in Nov. 2008, as my network has grown. Basically, click-through rates have doubled; it's a smallish group, to be sure, but the trend is in the right direction.
I've been letting my network of followers grow organically, letting them find me. I know the argument to jump-start or to accelerate growth: I could start following more people on a daily basis. But I as it is, I can't easily track some of the folks who most interest me. What would I do with thousands more. That's a commitment I'm not ready to make.
Meanwhile, check out "How Many Friends Can You Have?" by Sheryl Sandberg, Facebook's chief operating officer, which addresses the ways people can interact via social networks.