they held the extension system back possibly because it could have been a bottleneck or because they just didn't want to give you the possibility to use an extension that blocks their ads. however, they are working on the extension system (http://dev.chromium.org/developers/design-documents/extensio...) and you can already start creating your own extensions (http://dev.chromium.org/developers/design-documents/extensio... or http://dev.chromium.org/developers/design-documents/extensio...).

I think they are holding back on plugins because this is what causes the various speed bottlenecks that FF is suffering from. Plugins are nice until they slow down the browser.

Yeah. Firefox needs (soft) realtime [1] plugins.

[1] http://en.wikipedia.org/wiki/Real-time_computing

Whoa, you're right... they don't want adblock. I don't see any google ads these days. Not even on google search... (occasionally in gmail's webclips).

Could it be... that not having adblock is a major motivation for google chrome/OS? I suspect the market share of adblock is relatively small, but it's the kind of thing that can only grow... and unlike anything else that has been discussed, adblock directly threatens revenue.