Doom-filled warnings arrive from AT&T this week. The company says that without substantial investment in network infrastructure, the Internet will essentially run out of bandwidth in just two short years.

Blame broadband, says AT&T. Decades of dealing with the trickle of bandwidth consumed by voice and dialup modems left AT&T twiddling its thumbs. The massive rise of DSL and cable modem service in the 2000s has had AT&T facing a monstrous increase in the volume of data transmissions. And that’s set to increase another 50 times between now and 2015. That’s enough, says AT&T, to all but crash the system.

In response, AT&T says it’s investing $19 billion to upgrade the backbone of the Internet, the routers, servers, and connections where the bulk of traffic is processed.

Of course, AT&T is using this breathlessness in part to point fingers beyond simple broadband use. Web video (especially high-definition video) is the most commonly mentioned bandwidth hog. AT&T says video alone will eat up 80 percent of traffic in two years vs. just 30 percent now. One wonders how YouTube doesn’t collapse under the pressure. Hmmm.

Meanwhile, many are wondering whether this is prelude to AT&T announcing (or not announcing, but doing anyway) a traffic prioritization/shaping system like Comcast has been tinkering with… and which has earned it nothing but scorn. Net neutrality (which would forbid premium pricing for certain Internet applications and destinations) is a topic that continues to be hotly debated on Capitol Hill, and telcos are anxious to kill the idea since they’d love to be able to charge additional money for different kinds of web traffic. If the whole Internet is about to crash, well, that makes AT&T’s argument all the more compelling, doesn’t it?