Here is an interesting thought experiment:

Imagine you wanted to erase all the electronic data that exists about you. What would you have to delete?

Emails, instant messaging history, banking records, credit history, medical records, telephone calls, subscriptions, library books, comments on blogs, social network profiles, records of things bought and sold in online auctions, Flickr photos, Youtube videos and favourites, customised homepages like My Yahoo or iGoogle, saved bookmarks, online purchases, and so on.

Now compare this list to the list you might have generated 50 or 100 years ago.

Don’t worry, I am not trying to make you paranoid. I just think it’s interesting that so much data about us is created and stored, and I believe all this data makes our lives better and our economies more efficient. It seems that most people are willing to give up a lot of data in exchange for better access to information, provided that their privacy is not trampled too much. Aside from the occasional miss-step (eg Beacon), most web businesses seem to understand this pretty well.

The NYT Bits blog has a related post about this today. Check out the Digital Footprint Calculator.