"Ad blockers could block Google AdSense/ AdWords."

"could" as in "Adblock for FF works just fine for all who have installed it".

# Google may have scaling problems with increased traffic.

They do cope with this problem already at the moment I think. Why should they face this problem in the future?

# Google relies on bandwidth providers, so they’re vulnerable to their actions in that way.

OK, I agree.

# Ad blockers could block Google AdSense/ AdWords.

Well it's already there at the moment. But they can be creative, like ads on television. As nobody watch them anymore, product placement in the shows themselves are very popular. I'm sure Google find something like that...
(Or maybe when they dedetect you are using an ad blocker, your Gmail account will be closed ;-)).

# Google might have problems searching proprietary document formats on the web, e.g. if Microsoft adds indexing “protection” mechanisms to Word files.

This is unbelievable. As long as a publisher wants his files to be indexed, there will be a way to index that file...

# Search engine spam harms the results relevancy of Google

They already have spam detection algoritms and they will only improve...

# Google could face more privacy concerns, and a damaged reputation coming out of that.

Well, it's already a hot issue now. High trees catch a lot of wind but are mostly strong enough to keep standing... I don't think this will be too much of a problem...

# Google isn’t fully prepared if the mobile web takes off, as their apps don’t work across all mobile browsers.

I think they are doing quite a good job at the moment yet & it'll only improve in the future. It were in fact the first mobile applications I used on my mobile.

# Google faces click fraud.

Like the spam issue, they'll sure find a solution for this.

Adblockers aren't much of a problem atm because people aren't smart enough across the board to use them (or are just too lazy). Now if IE had a feature that blocked adsense but not adcenter ads, there'd be a problem.

There are many ways to do that: from editing the HOSTS file to disabling Javascript.

They forgot this one:

"Google's thousands of PhDs might be so keen on developing betas of cool new ideas that they might forget to maintain and develop their existing products."

Well, ad blockers pose no problem as long the ads are useful and not annoying. I am really an ad hater myself but Google ads were the first ads on the net I ever clicked on purpose more than once or twice. In fact for some keywords the ads are the only results that make some sense. So as long as that remains that way there will be not much reason to block them.

So in this case I have, as a search user, to admit that Google does very well. In contrast I block ruthlessly anything that is DHTML and does not allow me to see the content or is animated and distrcts me.

They did not mention anything of new ideas running away from the Googleplex to other start ups and I think the trust and retaining developpers may be a bigger issue than technology.