But they do include Steve Caplette, who was overcome with emotion on the day he wed Sally Petruzello. “I think it's fair to say that we know a little, but we probably don't know enough to have an algorithm that we think is really good,” said Dan Ariely, a professor of psychology and behavioral economics at Duke University.

“I knew which girls would date me in principle and which ones would not.

And I started thinking about where do I fit in, where do I fit in now?

Online dating’s Adam and Eve - Mina Jo Rosenbloom and Michael Linver found each other in 1965 with the help of a primitive computer dating program.

Four and a half decades after they were hitched by an IBM mainframe, they’re still married.

“So you look at all those tens of thousands of people, what are you going to do?

It's overwhelming.” Instead, e Harmony’s algorithm doles out just a few matches per customer per day. Computers are not good with emotions and feelings, said Essas.

A percentage of the daters who appear on e Harmony—and other dating sites—are not even paying subscribers, leading one critic to say that many users are, “flirting into the void.” Still, e Harmony is doing a number of things well, according to Dan Ariely.

“First of all, they have this million-question survey,” he said.

But Ariely says the problem is the simplistic way sites make us describe ourselves, using attributes that are easily searchable by computer but aren’t so useful in figuring out who we like or love.