It's good to know I am not alone: Many other people use Twitter a few times and can't think of a good reason to come back. With all the hype about Twitter's 140-character version of living, I'd gotten the impression that I'm the only one on Twitter who doesn't get why Twitter matters.

Not so, according to Nielsen data that shows 60 percent of people who use Twitter one month, even at its peak popularity, don't come back the next. While it used to be that 70 stayed away that improvement is not much to brag about--Twitter's customer retention is prone to peaks and valleys.

Twitter needs to be concerned about this, especially since both MySpace and Facebook have failure to return rates only about half that of Twitter. Put another way, 60 percent of MySpace and Facebook users come back the next month, about the same percentage that do not return to Twitter on its best months.

It is easy to think of reasons for this. Twitter is a one-trick pony. If you do not like tweeting or reading the tweets of others, there are not a whole lot of reasons to return.

Both MySpace and Facebook, for all their problems, offer more services than Twitter. It is easy to see how places where users can do more things could make the two services "stickier" than Twitter.

This does not surprise me. Twitter feels really light to me. Some people, obviously, become addicted but large numbers of others just walk away. That is not such a big deal right now as Twitter is in major growth mode. Growth hides all manner of sins.

However, if that growth mostly results in new users sampling and leaving, the growth will not last. Worse, it may be hard to get those unhappy users to return should Twitter ever expand its product features.

It is not clear whether Nielsen's measure of Twitter's return rate counts people, like me, who use a third-party application for their twittering. I do not return to Twitter nearly so much as I return to TweetDeck.

Today, it would be much easier for TweetDeck to make money off my use of Twitter than it would be for Twitter itself. Again, I do not see how these social networks ever make the big money that investors are betting they will.

To be honest, I am using Twitter mostly because I think "it's good for me," like some sort of social network vitamin. Like most good intentions, it will be interesting to see how long that lasts. Nevertheless, I am pretty certain to make it into next month.

I'm sure Twitter will be happy.

David Coursey tweets occasionally, and reached by e-mail using www.coursey.com/contact.