Chrome extensions can request only access to specific URL regex's, so they can be fine-grained about location, but the actual permissions tend to be coarse-grained. And as a user, you can't change the URL regex (that's some low-hanging fruit right there - users should be able to edit the URL pattern for any extension).

In some respects, Chrome apps are morphing to be general websites (e.g. with manifest.json and installing to home screen on Android), so hopefully things will move more in the direction of the web. There were also some hints towards on-demand permissions in the security talk at the most recent Chrome Web Summit, I'm not sure it's proceeding.