[jzl]

Not seeing any comments here about the most interesting part of the OP: how Ghostery ran tests disproving Google's claim about the length of ad blocking lists causing noticeable performance degradation. Yet in the mailing list announcement from Google that instigated this article they doubled down on that claim:

Increased Ruleset Size: We will raise the rule limit from the draft 30K value. However, an upper limit is still necessary to ensure performance for users. Block lists have tended to be “push-only”, where new rules are added but obsolete rules are rarely, if ever, removed (external research has shown that 90% of EasyList blocking rules provided no benefit in common blocking scenarios). Having this list continue to grow unbounded is problematic.

Yet, if there's a limit it will also be problematic. The lists only grow in size because of the cat-and-mouse game caused by ad blockers existing in the first place. If there's a size limit, that immediately gives a win to the ad servers because they will find a way to subvert the known limit.