I have heard that DHS has consolidated various databases and I would not be surprised if outgoing passport info is now shared with DHS by the airlines.
I have only anecdotal evidence to back me up, but I believe that US citizens are now being tracked and even flagged for extra CBP scrutiny upon return depending on their travel patterns.
See this interesting thread:
http://www.flyertalk.com/travel/fttr...ML/000420.html
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Pickles:
But the question is, does this loop back to the INS computers when you come back into the country, so that they would know automatically how long you were out of the country (or the time from your last visit)? I am certain it didn't for a long time, but now with the US-VISIT and the ability of airlines to scan your passport/green card/exit document, it might? Anybody know?</font>