They're the kind of delicious secrets whispered only by the very closest of pals. "I had a threesome with my cousin and her friend last night." "My uncle told me he used to date my mom. Now I wonder if he is my father." The difference is, these secrets can be read online, in their thousands, via the latest internet craze-within-a-craze, Secret Tweet.

It's a cyber-confessional where you can post, anonymously, the most bizarre and devastating secrets, about yourself, your sex life, your drug addiction, your desire for Big Macs - in 134 characters or fewer (even shorter than normal tweets). The secrets range from poignant to hilarious.

"My wife asks why I am moody. My secret mistress of 20 years just died of cancer. I feel so alone."

"I told my estranged dad I loved him - so he'd finance my car."

"I work in illustration and I can't really draw. I trace everything."

I've done a couple of Secret Tweets; it is oddly therapeutic. You fess up your worst secrets to strangers, and somehow you feel better: cleansed and purged.

The inventor of Secret Tweet is Kevin Smith, a 21-year-old graphic designer from Virginia. He started it as a "way for my friends and I to amuse ourselves". Now thousands of people are following, and tweeting. The site takes great pains to preserve anonymity - and censors the truly disturbing remarks. Smith doesn't make any real profit, but says he will continue, "as long as I find personal happiness".

These are modest ambitions. Yet Secret Tweet could just be a new kind of therapy for the 21st century. At the very least, it is addictive. As I write, someone has just tweeted this: "As much as I miss dad, I wonder if life isn't better with him dead."