My current reaction is still "this is not cool," but now I think I can better articulate why, and what Google can do to fix it.
The problem with the current Google authentication model is that not that they use one login ID across all their sites. This is useful, and makes a tremendous amount of sense considering that they want to build up a user profile. Everyone does -- Microsoft, Yahoo, Amazon -- this is normal.
No, the problem is that the Google authentication model has one "signed-in" state across all their sites. So when I log in to Gmail, I'm also logged in to Google Search, and in to Google Groups. I can't selectively "opt-out" of one or the other. In order to check my email on Gmail, I have to give Google Search my username. Same thing with Google Groups. And same thing with the next ten projects they are developing -- such as their version of Yahoo 360 (which I'd be curious to check out, btw).
Can you imagine if that by simply signing in to Amazon (which is required if you want to access your personal shopping cart, purchase history, etc), you were also automatically signed in to A9? People would flip. Well, perhaps people would mind being automatically signed in, but they should at least be able to sign out. Can you imagine if that by signing out of A9 you were automatically signed out on Amazon and could no longer access your shopping cart? Or that Amazon forced you to sign back in to A9 in order to finish your shopping?
Sign-in and personalization are great things. Amazon couldn't exist with out. A9 couldn't exist without it. Yahoo couldn't, Gmail couldn't, and so on. I have absolutely nothing against companies building up a profile of me -- but I want it to be application by application. I happen to trust Amazon and A9. Partly because I work there, but mostly because I've used Amazon for 8 years now and they have earned my trust. Hell, they've taken better care of my personal data and my credit card information than my bank has.
And it's not that I don't like Google -- I love products like Gmail. But I definitely don't know Google -- as a public company -- well enough yet, and won't for years, to believe that they deserve all of my trust across the board, no questions asked.
So the single sign-in model, with no ability to opt in or out site-by-site is a defect that, while it may be appealing to their stockholders, is certainly not appealing to all users. "Do No Evil" is a load of marketing b.s. until proven otherwise. I was willing to believe that motto based on the founder's reputation when the company was private, but I would never, ever just take it on faith alone when said by public company.
Fortunately, the fix is simple. Either allow users to "sign out" of one site, but not the other. Or offer a "generic" version of each service, such as A9 does with generic.a9.com.
Please keep in mind that I think search history is a great thing. I use it all the time on A9, and I think that many people would love to use it on Google. I don't believe Yahoo has implemented it yet, but I can't imagine it will be long before they do. I just prefer to be able to opt in, or out, of anything that tracks and records my personal data, that's all. And while I know you can "pause" the recording feature on Google (which I of course did), that doesn't change the fact they are still saving my username along with my search. Whereas on A9, I could just sign out if I wanted to (and still simultaneously use Amazon.com).