I certainly understanding wanting to have control over what you want private. But stars and forks are the main things I use to evaluate a project I'm unfamiliar with. If a project has 1000 stars and 100 forks I know it's pretty solid. If those metrics were disabled by default Github loses a lot of value, since the majority of users would stick with the defaults.
The counter doesn't have to be private, but being able to view exactly what one person has starred should have a privacy control. We do this at MusicBrainz with 'subscriptions' (to be notified when something changes). We give a number of subscribers, and those with public subscriptions are explicitly listed: http://musicbrainz.org/artist/10adbe5e-a2c0-4bf3-8249-2b4cbf...
