There has always been speculation on the Google Toolbar and if Google uses the data captured from the toolbar for ranking and indexing purposes. Lee Odden asked Matt Cutts of Google for a comment on those theories, in which Matt replied with a typical Google answer - we may. :) Basically, Matt hints that Google does not use the data for ranking purposes, because it can be too easily spoofed. But Matt said he wouldn't say they won't every use it or have never used the data from the toolbar. For the full, unedited response, visit Matt Cutts on Toolbar Data.
Matt believe this all springs from a recent thread at WebmasterWorld, I covered here. Where the thread discusses "traffic" being the new ranking factor in Google's algorithm. One way to determine traffic would be to use the Google Toolbar data. Google has been rumored to use the Google Toolbar data for indexing new pages for a while now. Matt did not comment on that rumor in his statement to Lee Odden.