Who knows more about me - Tesco or Google?

I like to think of myself as relatively savvy about how data about me is captured and stored. I know that by having (and using) a Tesco Clubcard I am offering up a veritable smorgasbord of valuable data about myself; not only where I live and what I like to eat and drink, but also what newspaper I read and - were I to take Tesco up on their full range of services - what clothes I wear, what car I drive (and when and where I fill it with petrol), what books I read, what DVDs and games I rent, what medication I take, my mobile phone and home broadband usage and even my bank balance and insurance provision. To what extent Tesco (or rather dunnhumby) joins the dots on all of this data is unknown although it's status as poster boy for successful CRM suggests, er, quite a lot.

Google is another company I'm aware knows a fair bit about me, although it wasn't until the launch of Google Dashboard last November, that I realised quite how much. Sure, there's my web search history (although that's possible to pause), but there's also my email, this blog (published using Blogger), my website stats, my online documents, my YouTube viewing, my RSS feed subscriptions, my checkout purchase history and - since I started trying out Google latitude - my location. Sounds a little scary when you put it like that, no?

The quality, convenience and competitive pricing (in Google's case, mostly free) of the products and services offered by both brands is what's keeping them dominant in their expanding (and no doubt soon to be overlapping) sectors. To what extent consumers will start factoring the volume, usage and transparency of personal data collected by these and other companies and how that will weigh against factors such as cost and convenience remains to be seen.

Of course, Tesco and Google aren't the only pretenders to the personal data throne. Through a combination of launches and acquisitions, Yahoo! now has access to my photos, email, bookmarks, conference schedule and - most potently - my social graph. The injection of users' social graph into the data mix is particularly valuable and Facebook is right at the sharp end of the personal data issues this entails, exacerbated by the rapid uptake of Facebook Connect, which is making its walled garden increasingly permeable.

Google Dashboard is a welcome baby-step in providing greater access to and - crucially - control over the personal data Google holds. It will be interesting to see whether Tesco starts moving more in this direction, whether by choice or legislation (clicking 'My Account' on the Tesco Clubcard site today returned the following message: "Sorry but an unexpected error has occured. We are currently trying to resolve the issue. Please try again.")

(Aside: Interesting to note that Tesco has dropped out of this 'Most highly-regarded business brands' ranking - although clearly the opinions of a selection of prominent UK leaders are likely to be very different to regular consumers).