I followed about ~10 people, and about half of those came from Twitter's own follow suggestions. I'd understand if I followed 2500, but it was a nominal and fairly reasonable amount.
If I were interested enough to create a Twitter account, I would start by following a bunch of people I'm interested in, RSS style. I most likely wouldn't post very much, if at all.
How many potential new users fit this pattern, are caught by the 'bot' filter, and are shut out of the platform, I wonder?