4 years before scandal, Herm Edwards waved to Bill Belichick's camera - NY Daily News
Spygate: An Inconvient Truth - CBSSports.com
Felger & Mazz: Cowher On ‘Spygate II’ & Patriots-Jets « CBS Boston
But personally I think the most salient details lie in that Belichick asserts truthfully that the Pats made no effort to conceal their videotaping and that the official game film validates that claim
Belichick insists Pats did not try to hide taping of opponents signals - NFL - ESPN
also that the Pats' practices were widely known around the league YEARS before the scandal happened, which suggests that the punishment that came down was not for the videotaping itself, but for the fact that Belichick continued to do it after the league office told him to knock it off in 2006.
When a player tests positive for PEDs, the leagues immediately suspends him. There's no 3-strike policy or anything like that. So either the competitive advantage the Pats got was nonexistent, or the league was at fault for letting them get away with it for so long.
Given the reactions that coaches who were in the know had, I'm leaning towards the former.