[darkstalker]

Ad blocking should be a core feature of web browsers.

[pbhjpbhj]

Web browsers developed by advertising networks or funded mainly through advertising networks aren't likely to consider it a wise addition to the core features however.

[psbp]

Most sites would go down this way. Very few sites could survive purely on donations or tiered pricing.

[aw3c2]

It is in Opera (or was, rather, until version 12).