I have no idea whether nor not Johnny Manziel has broken NCAA rules about making money off of autographs, but I know that professional autograph seekers are not an easy thing to deal with.
Manziel talked to SI's Andy Staples about one of the incidents reported on recently, the one in which he signed some items in a hotel room for free before allegedly his buddy Nate Fitch later asked for payment. He describes getting to his pregame hotel room when a guy with stuff just elbowed his way into the room. This guy had to have been either camping out near the room or stalking him from the lobby in order to do this. That's pretty bold.
It doesn't surprise me a bit to hear it, though, after all of the stories I've heard about Tim Tebow's experience. This story from June, 2007—a couple months before Tebow even made his first start—tells of an autograph hound waiting for him at his dorm hall. By 2009, hundreds of people looking for autographs waited outside every practice. He tried to manage things by restricting his signing to just kids, but then the professional collectors just gave kids things to get signed.
Manziel is not the only player in today's game with his memorabilia being sold out in the open. Run down some of the big names from the preseason All-SEC team—T.J. Yeldon, Todd Gurley, Amari Cooper, Jordan Matthews, Jadeveon Clowney—and things they signed are up on eBay. Even Robert Nkemdiche, who hasn't played a down yet for Ole Miss after being the nation's top recruit, has a few things available.
Autographs really do seem like a good first step for the eventual deregulation of amateurism that's going to happen. It would be a good thing because players who can get paid for signatures are likely to set up many sessions where they can get paid to sign things. That fact means the supply of their autographs will go way up, which will reduce the incentive for strangers to elbow their way into players' hotel rooms.
I can't imagine what it must be like to be someone who gets hit up for signatures all the time like Manziel. The temptation to try to make some money for yourself must be enormous when there are plenty of people profiting greatly off it without providing any value back. Schools, which are getting more and more explicit about profiting off of players' likenesses, at least provide players with tuition, room and board, food, health care, and a platform on which to become famous. There is plenty of room to argue whether that's just compensation for the value that players create for the schools, but at least it's something.
The "eBay guys", as Tebow's family called them, give athletes nothing in return because NCAA rules prohibit them from doing so. That's a pretty rotten deal, especially considering that some dealers actually would if they were allowed.