Ever locked eyes with a stranger on a train or in a store, become quickly intrigued, and later regretted not even saying "hello."
In a fast-paced world growing ever faster online, the Web is replacing the newspaper personal ad as a place where people can act belatedly on that moment of magical chemistry -- with some fleeting encounters even leading to marriage.
At social networking and advertising site Craigslist.org, a subsection called Missed Connections, is rapidly becoming a destination for second chance encounters, and its ads tell tales of infatuation, hope, frustration and love.
Craigslist's Chief Executive Jim Buckmaster said he had heard of several marriages forged through Missed Connections which was set up in 2000. Use of the site has surged in the past three years to 75,000 new postings a month from 18,000, with San Francisco the biggest market then New York.
"It is a long shot but hope springs eternal -- and people seem to have a weakness for long shots," Buckmaster told Reuters.
Ads on the site read like this: "Birmingham girl with Stella Artois at Gristedes!!!! I do not know why I did not invite you to drink beers with me...I hope is not late, I would love to."
Or this: "Confused Brunette On The A Train This Morning: You came into my A train, but quickly turned around and exited. I wish you stayed."
What are the chances?
But in New York -- a city crammed with eight million people -- what are the chances that the stranger from across the train will log on to the site that day, find the post and respond?
Ask Mark Svartz. While standing in line for two hours to have a book signed by American writer Jonathan Safran Foer, Svartz, 27, chatted with the girl standing in front of him. They did not exchange even their names.
"The next morning I realized that it probably would have been smart to get a number," he said.
Like the 15 million other people in the United States and Canada who use Craigslist.org each month, Svartz, an advertising executive from Manhattan, sometimes reads the Missed Connections posts for kicks. Now he had a reason to make the leap from voyeur to participant.
"I remembered she had purple slipper shoes on, so I wrote: 'Girl with purple slipper shoes. We spoke at Jonathan Safran Foer signing. Sorry I didn't get your number. Let me know if you want to talk.'"
"The next day I got a message from her, an email saying she was purple slipper girl."
But it's not just those seeking relationships who turn to Missed Connections. Some are using the site to end them.
Another ad on a recent day aimed at "Adam" reads: "You are the most confusing guy I've ever dealt with -- part of me wants to run into you at work and then part of me wants to just never run into you again."