Hit count admin pages being indexed by google

I have a strange problem whereby a blank page simply displaying the hit count of a post, is being indexed for each post in google.

An example:

wp-admin/admin-ajax.php?action=ajax-hits-counter-increment&post_id=270&t=

Any idea why this would be happening? How would google find such obscure links?

I just blocked admin-ajax.php in robots, do think this will sort it?

http://wordpress.org/plugins/ajax-hits-counter/