How many of these are from one-time spam accounts? I know I get people following me from time to time who follow a bunch of people hoping to get reciprocal fol

How many of these are from one-time spam accounts? I know I get people following me from time to time who follow a bunch of people hoping to get reciprocal follows, then send out a spam tweet and move on to another account. It probably doesn't account for the majority of these, but I would guess it's non-trivial.