I think the biggest threat is Jack Thompson (And people like him) and uninformed journalists.
Basically, both are doing the same thing: Spreading complete lies to further their own gain. With Thompson and people like him, it is some political or "religious moral" reason. For the journalists, it is all about ratings.
The journalists are particularly bad, because it is an example of what I HATE about the media: The concept of pulling things out of your ass just for ratings. Whatever happened to integrity in our news networks? Oh, I remember. That got pissed on around the time that everyone started dicking around and paying attention to celebrities more than actual news.
The journalists are worse than people like Jack though. The typical American has never heard of Thompson, and likely never will. However, when someone like Fox News shits out a steaming pile of lies and misinformation then people take notice. The Fox segment on Mass Effect is proof, as they based EVERYTHING they knew about the game off of a rant by some bigot looking for attention. Worse yet, they bring in a woman who has never even see a video game before as some sort of "expert" for a debate about Mass Effect and how bad and distasteful it is. Now, anyone who has ever played or done research about the game would see that it was all a load, but the average non-gamer American would listen to all this stuff about Mass Effect being a "porn simulator" featuring "full digital nudity," "the most realistic sex acts ever conceived," and "violent orgasmic rape," and be really concerned. This makes the game look very bad, and smears the name of the industry just because someone with an agenda started spreading rumors on the Internet and a group of ignorant journalists find it, think it will make a juicy story, and run with it without bothering to check their sources and do research...something that any respectable journalist SHOULD be doing instead of wanking off to potential ratings.
Really, this is just like someone making up a story about how a respected local surgeon rapes his female patients when they are under anesthesia and putting it on the nightly news. It smears that person's image by spreading outright lies for everyone to hear. Now, some might argue that a news network spreading lies about a video game for ratings is no where near as bad as that example, but really, it is. You have to remember that some of us work in the industry for a living, and when news networks spread lies about games or the game industry, it hurts us. Not mentally, mind you, I think some of these things can be rather hilarious, but then we have to deal with all the potential backlash and outrage based on something that just isn't true. Now we have to deal with the random angry mother groups and intolerant religious fanatics ragging on us because they heard a bunch of lies on Fox News.
It also hurts gamers, because now we have to watch what we do or put into games to avoid random hate. Which is pointless anyway; a lot of these people just make up random bullshit and get it passed off as fact.
In any case, uninformed journalists are one of the biggest threats to the game industry. People listen to what they hear on the news, even if it is bullshit they made up or spun from half-truths to make a potential rating booster. The more lies are spread about the industry or certain games, the longer the general public will have negative opinions about them. That in turn means that games will be everyone's favorite whipping boy for longer because it is easier to manipulate the masses to hate something they have a negative opinion about in the first place than to attack something that people have a better understanding of.