My guess is that more than one reefer was burned over the lockout by NFL players. The NFL doesn't blackball dudes because of weed. If it did, Sapp would have never been drafted. Moss never would have been drafted. Hell, half the League prolly would have never been drafted.
When you sign an undrafted free agent, you have virtually no downside because you can just cut the dude. My guess is that ending up in KF's doghouse cost DJK a fortune. If DJK got busted under those circumstances in the offseason and didn't cause a crapstorm before the bowl game and ended up getting in Ferentz's good graces somehow, things may very well have ended up differently. But I have a hard time believing a guy can go from breaking Timmy D's record as Iowa's all time leading receiver and being a dude who lit up the night in Columbus on a 100 yard KO return showcasing pretty sick speed to untouchable by the NFL over a marijuana conviction carrying a $315 fine in the year 2011. No way.