Avoid spamming and phishing attacks with unique usernames

Hackers could track the person behind the usernames. Using a method of cross-referencing usernames across different sites (eBay vs. Google vs. Facebook vs. Twitter) they're able to accurately match multiple usernames to a single physical user or accurately targets spamming and phishing attacks to your email account.

If you want to check how unique is your username or how linkable are your usernames you can use the Username Uniqueness Calculator developed by Planete Team of INRIA (Institut National de Recherche en Informatique et en Automatique). I tested it and I found that all my usernames are unique (with "entropy" values beetwen 40.05 et 69.84 bits) and they're not linked at all.

Links :

Username Uniqueness Calculator

New Scientist's article