It's a good point, but it will push the bounds of the creepiness factor even further. On one hand, it's part of the evolution from your queries to your mail to your files, but each level gets more and more personal. It's also interesting that Google hasn'

Jeremiah’s comment on yesterday’s post about Google’s upcoming storage service is worth a post of its own. He wrote:

The
big opportunity (if users will allow it, or skip terms of service) is
the ability for Google to sell ads on top of content within a Gdrive.
Eventually, this will continue to become a commodity market, and could
flip over to beg for consumers to upload content (data is key for
serving ads). I still predict that some online data storage company
will figure out how to pay customers to upload data to serve up ads.
Have you ever seen those advertisements that give away computers for
free to lower income folks? They get access to a 1000 dollar laptop in
exchange to being exposed to heavy advertising.

It’s a good point, but it will push the bounds of the creepiness factor
even further. On one hand, it’s part of the evolution from your queries
to your mail to your files, but each level gets more and more personal.
It’s also interesting that Google hasn’t tried monetizing its free
Google Desktop in any direct way; rather, it nets Google more
registered users and more user loyalty for its services.

Interestingly, this came up in a column a couple years back, "Google Talk Pays For Itself":

Once you’re registered for one service, the barrier to register for
another is minimal. As a Gmail user, I didn’t think twice about trying
the personalized home page, Google Desktop 2, and Google Talk. All of this keeps me in a Google
bubble…. That means it keeps getting easier to search on Google – another barrier lifted. This gives Google’s advertisers more keyword inventory. And that’s just step one.   

Steps two through 50 involve ad targeting, starting with demographics
and then going by search history and then graduating to behavior and,
one day, Google
discovers it’s so darn smart it just starts telling you what you’re
looking for before you even search. It becomes your personal valet.