General-purpose Chrome extension enumeration[1] should have been fixed some time ago, maybe here: http://crbug.com/45876

There are still issues with fingerprinting based on specific attributes of a particular extension (for example: [2]), however.

1: http://www.skeletonscribe.net/2011/07/sparse-bruteforce-addo...

2: http://blog.securitee.org/?p=277