Well?

I don't know how one can arrive at a figure, other than attempting to read every Twitter account there is and tallying the results.

I've blocked loads of people myself, you have to to make it usable.

On Facebook I've currently blocked 1786 people. It would be a lot more but I brought in a rule of never reading the comments on anything political - before that I'd end up blocking the first 20 commenters on each post.

I don't think anyone's ever blocked me.

But I could be wrong.