Actually they've always done this - check up to make sure you leave.
Any tourist should remember not only filling in the "are you a criminal" card on the way in, but also the "I'm leaving, honest" card on the way out. The cards are matched, and no doubt hotel rooms sacked if inconsistencies are found. Or not.
One of the funniest immigration conundrums happens here in cheery Alaska.
We have no immigration courts, no prisons large enough to hold those awaiting deportation hearings (that's right, the benevolent US government has always stuck asylum seekers and those with questionable immigration status directly into the nearest maximum security prison - sometimes for years, with no trial or charges ever presented).
So they round up the usual group of suspects every couple years, give them their court dates and ask them to promise to show up in Seattle. They're then released until a few years later, when they'll go through the whole inconvenient process again.
As a legal immigrant I'm often quite disgusted with the behaviour of the immigrant Nazis.
The latest piece of genius legislation is making the rounds in the Alaska State Legislature as we speak.
They propose including immigration status on all driving licenses, so the police can arrest illegals.
Of course the reason I say genius is because you can't actually get a driving license without a valid Social Security card and some tamper proof ID to back it up. You can't get a Social Security card without proof you're in the country legally, and finally the only people allowed to demand to see the already mandatory-to-carry-at-all-times biometric Alien Registration Card are the DHS.
So effectively a piece of legislation to create a second, less difficult to forge, piece of ID as well as the lawsuit enabling addition of allowing hillbilly cops to detain you if they don't like the word immigrant.
Money well spent I say.
Wonder where these guys grand parents came from.. oh that's right, they were immigrants..