CAT | Biometrics
The New Scientist has an article on the FBI’s Next Generation Identification (NGI) program.
It started out as a project to replace the old fingerprint database, but will now include biometrics, DNA, voice prints, and facial recognition.
The idea is to database all the mugshots so people can be quickly identified after arrest, or possibly so surveillance video could be compared to the database to identify possible suspects.
Obviously lots of civil liberties issues here, but still a very long way from the paranoid hollywood inspired rantings about real time global surveillance with integrated biometrics.
While the technique would not allow them to identify your anonymous emails in an ocean of others, that is rarely the real world threat scenario.
In many cases there is a relative hand full of likely authors of a given email or group of emails. It is often possible to gather large samples of emails known and acknowledged to be from the likely authors. In that case this technique has a small group of targets and excellent training materials which allow for very high levels of accuracy (the authors of the paper claim 80% – 90%). That is probably enough to get a warrant to search your home and computers.
Unless you have been unusually careful, the gig is probably up by then. Remember, this might not be for criminal matters. It many cases this would come up in whistle blowing or other non-criminal situations.