For months, we've heard that Twitter, the fastest-growing social network this side of Facebook, was at the tipping point of relevance. Well, maybe it's more like the fastest growing social network this side of MySpace.The vanishing point is that spot in the horizon where the sea meets the sky, where a ship's tallest mast blends indistinguishably into the fuzz of clouds and froth. Or where a phenomenon dissipates into the milky froth of a cappuccino and everyone realizes that there's no there there.

Maybe it's just growing pains and Twitter will right itself, but the last month has been unkind to Twitter. The most recent setback is a glitch that prevented the service from providing real-time search. If Twitter is going to last longer than a twinkle in co-founder and de-facto spokesman Biz Stone's eye, this is the kind of service it has to get right so it can charge businesses for the right to use it. I can't wait for Stone's next apologetic blog post, likely titled something like, "Holy F**dback."

There's also the fact that, for what seems like the fiftieth time this month, it turns out Eve doesn't know @Eve from Adam. Again, if businesses are going to trust the comments are genuine -- and that Tweets from the boss aren't actually from @rival -- they have to work this out. And that won't be easy considering that Twitter needs to have a frictionless sign-up process. They can't very well ask for a credit card for authenticate purposes.

Add to the list the mind-numbing idea of a reality show where contestants receive Tweets from the audience that help them win the treasure hunt, unmask the false millionaire bachelor or tell them when their spouse is cheating on them. All good for a lark until @Ashton threatens to quit Tweeting if anything like this comes to pass.

Indeed, of all the misfortunes to have befallen the chirping social network, the much-bandied stat that Twitter tweeters throw in the towel quickly might be the worst. As cell phone companies will attest, you can only achieve so much growth when your customer base is churning out from under your feet.

And unlike cell phones, Twitter isn't exactly catching fire with Generation Y (its biggest demographic is the 35-49-year-old set). My 13-year-old daughter just got back from an overnight with her entire grade, a night in the country under the bright stars, howling coyotes and iPhones buzzing with Facebook updates and viral YouTube hits.

"Does anyone in your grade use Twitter?" I asked her.

She rolled her eyes. "No. That's for old people," she said.

I realize I might as well have asked her about MySpace, that other high-masted phenomenon that has tipped over the cusp of the curving globe in time for the next social network to be born.