I'm pretty sure almost every team does this. And while the Pats are my "B" team I'm glad this happened to the Pats first - now all the other teams that pull the same crap are on notice and when they get busted the fines are likely to be even stiffer. The Dolphins pretty much admitted to stealing the Pats signals last season and the previous commisioner saw no problem with it.
And Mangini... well he has earned the "a".
Teams steal signals all the time. They use binoculars, etc. That's not what's against the rules.
The reason the Patriots got in trouble is because they were using video cameras to record the defensive signals, which is clearly a violation of league rules. There is a grey line ethically, because the spirit of competition should disallow the stealing of signals, but it's not in the rule book. Video-taping signals, however, is, and the Pats are paying for it.
Other teams might have done it in the past, but I doubt it's prevalent. I mean, Belichick is highly regarded as a genius; if he got caught, then it must not be that easy to get away with.
No matter, though. I bet the NFL allows radio equipment in a defensive player's helmet for next season, which the coaches have been lobbying for for several seasons, and getting closer and closer each year. That will put an end to stealing play calls with video equipment. Then teams can focus on stealing audibles and hand signals from the quarterback.
