Jeremy Zawodny (http://jeremy.zawodny.com/blog/archive
One possible application for this would be for Google itself to run a service allowing very highly personalized spamming or in-frame ads to your orkut account based on a combination of Google searches and personal profile data.
I think the framework is already in place for this.
This is pretty sophisticated, and it could be done in a way that's unobtrusive and not particularly nefarious.
However, simply the fact that they >can< correlate searches to identity is possibly a bad thing, even if they only make "benign" uses of it. If the data is there, it's waiting to be hacked, leaked, or abused. The fact that they've made no public mention of how or whether this information is to be used is worrying to me.