A quote directly from twitter: Following (account-based): Once an account is following 2,000 other users, additional follow attempts are limited by account-specific ratios.
I couldn’t follow more then one or two a day for over a year and it happened as soon as I hit 2000, I took someone’s advice and had my followers and following almost the same number but that didn’t help. BUT recently I went back and unfollowed alot of old or inactive ones and so far I’ve been able to keep going. It’s gets harder at the 2000 mark. I won’t follow more then about 50 a day because I am nervous to be restricted again. What sucked about it was I wasn’t able to follow back people so I would get these notifications saying someone followed me and had to look like a jerk and never follow back. – Laura Carter