I haven't heard ANY reports about the teams that I follow doing it. This league wide epidemic argument is a bit exaggerated from what I've heard. Seems to be linked to Bellichick and his coaching tree. Also, just because it happens doesn't mean it's right or acceptable. Stealing signs in baseball happens but it isn't condoned. It's a big deal when someone get's caught doing it.
But, taping signals is bad enough but if they are found out to have been taping practices of other teams, I don't see how that can be defended in any way. Tendencies is one thing but having the plays and signals for a particlar game is out-and-out cheating. I don't subscribe to the "if you a'int cheating, you ain't trying" point of view. Lombardi, Landry, Shula...those guys won without sinking to the levels the Patriots have. It's not impossible to do and it should be deplorable to anyone who is a fan of sports.
If the taping was of no benefit, why were the Pat's doing it and why were they fined to the maximum under league rules for getting caught?