>Presently there isn't a national database for ALPR but >they're working very very hard to make this a reality.
Maybe not a government run one, but there sure are private ones. Companies like Vigilant (http://vigilantsolutions.com/) probably have over 1-2 billion plate reads nationwide, and law enforcement agencies can get free access to it (http://nvls-lpr.com/nvls/).
There is also a project which was funded by National Institute of Justice which tried to allow all ALPR systems to insert data into a single repository. That's the present problem right now - two neighboring jurisdictions might have different systems.
Maybe not a government run one, but there sure are private ones. Companies like Vigilant (http://vigilantsolutions.com/) probably have over 1-2 billion plate reads nationwide, and law enforcement agencies can get free access to it (http://nvls-lpr.com/nvls/).