It's in danger of collapsing under its own weight.

Even by Internet standards of hyper-growth, there has never been a phenomenon like Twitter. Less than a year and a half ago, Twitter hit 1 million users. It now has 44 million, a rate of expansion so rapid that if it could continue growing at that speed it would in another year and a half be used by everyone on Earth. It is impressive not just for the sheer number of users but for the share of mind it has carved out, from the national elections to its starring role in Iran's election protests. Twitter has become so ubiquitous so fast that it's almost impossible to imagine it disappearing.

But it can. The irony of Twitter is that even as it becomes more pervasive, it is in danger of very quickly becoming markedly less useful. Twitter is in danger of collapsing under its own weight. Not because of its problems keeping up with traffic—those are solvable—but because the volume of material that Twitter unleashes now puts impossible demands on its users' time and attention. The problem, in a nutshell, is information overload. The more Twitter grows and the more feeds Twitterers follow, the harder it gets to mine it for what is truly useful and engaging. Even as Twitter reaches a peak in the cultural cred cycle, it's time to start asking how it can be saved from itself.

I first started wondering about how much attention folks are paying to all their Twitter feeds about a month ago, when one of my stories was mentioned on the Google corporate Twitter feed. At the time it had close to a million followers (and is now at more than 1.3 million). I would have expected the link in the Google tweet to generate a substantial amount of traffic to the story. It did not. It's hard to pin down an exact number, but judging by The Big Money's logs of how readers came to the story, Google's tweet seems to have led about 100 to 200 people to click the link and read the full story.

I'm happy to have even a few additional readers, but this is a very, very small number. More important, the number of people who click a link in a tweet is probably the best proxy we have for a measure of how engaged folks are with Twitter. The small number of people clicking on that link seemed to me an early sign that we've reached a point of Twitter saturation, in which the result of more people following more feeds adds up not to more communication but more noise.

In the recent history of technology, we've often been told of the value of "network effects." Much of our experience of technology is with positive network effects and increasing returns as more people take advantage of it. An obvious example is e-mail; the more people use it to communicate, the more useful it is. Yet network effects can also be negative. A park that is popular becomes more vibrant and appealing. But a park that gets too popular is just crowded. Twitter's growth has been so rapid that it is clearly bumping up against the limits of its usefulness. It is not only increasingly full of noise, but the sheer volume of stuff coming through the Twitter fire hose renders even what was useful much harder to pick apart and make sense of.

A recent and heavily publicized study showed that the overwhelming majority of Twitter tweets come from just 10 percent of its users and that most Twitter users send out less than one tweet a week. Twitter skeptics seized on the study to say that the Twitter meme has been overblown; one memorable headline even took the study to mean that "Twitter is almost completely useless." This isn't really fair. For one thing, the Iranian protests proved without a doubt that in some situations Twitter really is stupendously useful. More generally, there's nothing wrong with signing up for Twitter and sending out nothing at all. Just because most people don't write books doesn't mean that books are useless. Just as most people are happy simply to read books, many Twitter users may prefer to follow a few prolific tweeters but rarely send out anything themselves.