I have a little conspiracy theory. First there was the Gmail account: few people had it, many were afraid of it, some would pay money to have it. Then there was the Google account: you already had it if you used Gmail, it wasn't very useful. Then Google started to add some services to Google account: Froogle WishList, the personalized homepage, the personalized search and many more.
Before creating the Google accounts, Google used to rely on cookies to save preferences. The new accounts are a way to save personal stuff and all Google services have something to save. But not everyone visits Froogle Wishlist, or Search History, not many people have heard of Google Spreadsheets or Picasa Web. But everyone has heard of Gmail and a lot of people use it, although it's in beta and it still requires invitation. I think Gmail was created to make people have a Google Account and remain logged in.
What's the most common activity on the Internet? Email. What's the most visited subdomain on Yahoo? Yahoo Mail. People check their mail all the time and won't log out too often.
Now all Google services will migrate to Google Accounts (AdWords and Orkut have migrated; Blogger and Writely are next) and you'll have more reasons to be logged in. But why would Google want to be logged in? By combining the information from all these services, Google can know more about you, improve the search results and ad targeting.
This is just a conspiracy theory that passes through my head everytime I see my username above the search results. I could delete the personalized search service, but I would still be logged in.
If you're wondering about the picture above, Google accounts' codename is GAIA, which is the goddess of the earth, in the Greek mithology.
This quote is from Susan Mernit (September 2004):
"Google's much speculated integration of services seems to have moved forward a step with the further integration of Google Accounts, a control center for those of us who subscribe to any combination of gmail, Google groups and Google search or news alerts.
Apparently, this new feature's been live for a week, but I was shocked when I tried to sign up for a news alert and Google immediately defaulted to my gmail account--not the place I'd planned to put it.
Clearly, the moment when gmail is the underpinning to link all the services together--including Blogger, Picasa, and Froogle--is coming closer., And that is going to make A LOT of people pay attention."
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