We're using 10% as a very conservative estimate actually. We've been measuring adblock data for 9 months now across several hundred sites, many of which are very large. The current average blockrate across all these publishers is 26.1%. These are the guys who are so acutely affected that they signed up to us in the first place, but it gives you a good idea.

A fair estimate of a minimum value is the block rate on sites that are non-techie, e.g., lifestyle (12% blockrate) and news (16% blockrate).

We'll be doing another post soon revealing all these numbers and our methodology in collecting them in detail.