Arnold Kim reports on MacRumors (and I can confirm) that the iPhone no longer prompts users to rate an application upon deletion. Developers have complained about this since it was introduced because it skews ratings downward.

I personally remove applications from my iPhone all the time, just as a way of cleaning house. There are many apps that I use rarely and therefore only install on my device when I actually need them. I usually use the prompt as an opportunity to rate these applications. So for me this means I will likely never rate another application again.

But for the majority of users and developers, this is a good thing.