Guys, I was at ORD
(27L) all day on Sunday (March 23) without any problems. There were even a few other spotters there as well. The only time I was afraid that I'd be kicked out was when a black detectives car circled the lot a couple times - he drove past me, but didn't stop.
There was even one guy who was completely out of his car all afternoon (parked in the restricted area of the USG lot) just watching planes go by - the cops didn't even talk to him.
I was fully expecting to get chased away that day, but it was cool. Maybe because it was Sunday (less traffic)?