Tucked into a sunny booth in V Bar in the West Village, Mr. Schechter pushed aside a panini and flipped open a laptop, revealing a spreadsheet of dates proposed and accepted by the site’s members: “How about we attend a swing class and wine tasting?,” “How about we grab a beer and play a game of ping-pong at SPiN?,” “How about we check out Ninja New York, a Japanese restaurant with ninjas for waiters in the meatpacking district?”

“You can tell so much about somebody based on the date they propose,” Mr. Schildkrout said.

Both he and Mr. Schechter have profiles on HowAboutWe. Mr. Schechter’s page says he possesses obscure knowledge about chakras. His latest date proposal? “How about we learn how to read tarot cards (after buying a set somewhere in Manhattan) and practice at the 169 Bar?”

Scanning the site’s database, he observed, “There are trends and hot spots.”

Indeed, Coye Cheshire, an assistant professor at the School of Information at the University of California, Berkeley, said strangers have been shown to gravitate to the same things at the same time as preferences are diffused among groups through word of mouth or social networks. “It’s not surprising to see these trends ebbing and flowing,” he said.

Samuel D. Gosling, a psychologist at the University of Texas at Austin, said that the cuisine trends could occur because members of the Web site value doing the latest thing  until it becomes widespread. (After all, they were early adopters of the site itself.)

“It might be that you only want to do it if 1 percent of other people are doing it,” he said. “You don’t want to miss the trend, but you don’t want to be behind the edge. That sort of decision strategy would result in that pattern.”

That New Yorkers on a dating site would be drawn to similar activities can be explained in part by a sociological principle known as homophily. “It’s the idea that similar people tend to value the same things as other people like them,” Professor Cheshire said.