What Google knows about me

I've had some disagreements on the interwebnet about the benefits of centralised data vs a more federal model. My view is that it's far easier to throw resources at securing important data if it's all held in one place rather than scattered around in small pockets. Many commercial organisations operate in this fashion, but when governments try to achieve it, it's met with hostility and suspicion.

Google have recently created an interesting tool which I think illustrates my point of view. The google dashboard:

https://www.google.com/dashboard

Shows you everwhere you're identified on the various google systems, and what information they hold about you. It also diferenciates between what's private and what's public. It's very effective, I hadn't remember granting a twitter app 'log in on my behalf' permissions, which showed up on the dashboard, and I was able to block it's access. Very effective, and I'd love a similar ability from government, log in, click my name, and have the application list everything the government knows about me. Only really possible with some sort of central identification of who I am, such as an ID card.

Of course, the danger is someone getting access to my single google account, and therefore having access to all this stuff. My view is that I'd happily pay to make this account more secure than worry about lots of little accounts all over the shop.

What do you think, is this kind of centralisation a bad thing?