Democracy requires a healthy news media to keep it in check. A healthy news media requires money to pay its top reporters to go investigate stories. The Internet is sucking money away from TV news organizations and traditional newspapers and news magazines.
Unfortunately the free news distributed on the Internet doesn't make much revenue for any individual company. The ad-supported model is too weak, and growing weaker as the amount of content grows faster than the number of advertisers. So eventually there will be no funds to pay investigative reporters. The so-called "news" will be whatever information is cheapest to gather, such as lies from the people in charge. That will doom democracy. Obviously we're more than halfway there already.
Once democracy is completely broken, crazy dictators will find it easier to get nukes and then it's a slippery slope to total nuclear annihilation.
A recent cover story in Time suggested that the solution for creating a profitable news media, and thus saving the world (I added that part), was a generally accepted system for micropayments on the Internet, so news could be purchased as easily as music on iTunes. The technology part is doable, but in my opinion most of the public will prefer free news sources over paid news even if the quality is vastly different. So the Wall Street Journal, for example, could continue doing great reporting as a subscription service but too few regular citizens would read it to make a difference.
The other way things could go is that news media companies will merge until a few moguls control all of it. That would solve the profitability problem. But at that point it won't matter if the few moguls have the money to pay investigative reporters or not because the moguls will effectively control the world. The last thing they'll want is accurate reporting. With any luck the media moguls will back puppet leaders who are benevolent dictators. That's our best hope.