It seems like they are checking for opened bottles and such. When I went through security at BWI, they made me take a drink of the coffee I had bought. But when I was coming back from SAN, with a sealed water bottle, they didn't say a thing.

In other words, if terrorist wants to release some poison on a plane, all he has to do is make sure the Coke bottle he uses to do that is sealed and he'll be able to do it. Now, how you get the poison into the Coke bottle without breaking the seal...well, that's something I don't know how to do.