Question or two about Pass Interference...

Whether it's college and professional ball, is it just given that the refs allow contact between the receivers and defenders? Is that what they refer to as "handfighting" and it's allowed since both guys are doing it? Rarely do you see one-on-one coverage downfield in which there is no contact. I watched that play a couple of minutes ago when Eli tried to hit Evan Ingram down the middle of the field. There were two guys hanging on him, but nothing was called.

Whether it's 5 or 10 yards, the refs could call illegal contact on virtually every play.