Exactly. When you are using my machine I reserve the right to track you. There are lots of database driven sites where every page is unique and tracked. I work on one where the server logs are loaded directly to the database and there is an interface that "follows" a visitor through the site 15 to 30 seconds behind. To correlate the data longterm to identify individual users from the pool of visitors would be trivial. Not worth it in our minds, but I am sure others are doing it.