Well a few thoughts on it.
For free apps. I don't think it matters so much. Since I can try it out if I want.
But for pay apps, for the average user (most iPhone users), deleting a paid app is a significant deal. Remember, the vast majority of users aren't trying to figure out which apps they want to fit on their 9 available pages. I think a delete for a paid app from an average user is a significant event and think those thoughts being reflected in the rating is not a bad thing.
I don't know if I would expect a lot of apps to be unfairly rated with this.
arn
Surely, if anything, they're more likely to be harsh with paid apps though?
I'm not sure about whether a lot of apps would be unfairly rated or not, I have concerns that it could happen (see my first post on this thread) due to that good old thing called human nature - you're asked to rate at a time when you're bored enough of it to delete it, even if you liked it. If you're asking for feedback on what is essentially a negative action (deleting) then it follows, in my opinion anyway, that the feedback is more likely to be negative, regardless of what the consumer actually got from the app in the first place.