Sure, being an "IT professional" I can turn cookies off but most Web surfers aren't IT professionals and do not know what a cookie is- much less how to turn them off.
I dont want to seem rude, but have you ever written a cookie?? If you have, then please explain why you would store a clients previous search's or sites visits, on a client-side cookie.
I could probably come up with over 5 key reasons why this is not the way to track users.
Another key thow off is, why the use a toolbar?? Cookies could be stored on regular web searches, just like Yahoo does. hmm. Any IT professional would recognize that the reason Google uses a toolbar is to provide real time data, similar to the likes of Aol's AIM.