Some entity called "TrueSciPhil" tweeted to me the following list of philosophers on Twitter based on their total followers. The total number of followers is a bit misleading, since it seems to be affected by how many other twitter users the philosopher follows (if you follow someone, they often follow you in return, or so it appears). By the ratio of "followers" to "following," Daniel Dennett is far and away the most genuinely "followed" twitter philosopher, with a ratio of 3,231 followers for each person Dennett follows. Alain de Botton, by contrast, comes in at 649 followers for each person he follows. Peter Singer does better than that, with a ratio of 898 to 1. Patricia Churchland clocks in at 163 to 1, Peter Boghossian at 261 to 1, and A.C. Grayling at 98 to 1. I clock in at 113 to 1, while Luciano Floridi registers at about 2 to 1.
From this, I think it's safe to include that this list is meaningless.