I'm not sure... as a single data point I measured usage on the Mibbit main client for a while (Mainly early adopter fx3 tech types), and it was 8% or something for the main client.
Of course it isn't too important as adblock is useless in blocking all but the most simple adverts.
In the general population the % is probably much much lower though, so you're right - probably not worth worry about until you're a very big site.
It's more the antisocial attitude I disagree with.
