Facebook raised privacy concerns when company officials admitted to manipulating 700,000 users' News Feeds for an experiment. Now, it turns out OKCupid also explored the compatibility of its users.

"If you use the Internet, you're the subject of hundreds of experiments at any given time, on every site. That's how websites work," wrote OKCupid president Christian Rudder in a company blog post on Monday.

Rudder admitted that all users of the popular dating site were involved in three experiments without their knowledge.

The first experiment tested the "blind date" feature, which launched more than a year ago. On its first day, all profile pictures on the site were removed. The experiment showed that communication worked better without photos; 44 percent of users were more likely to respond, and exchanged contact information quickly with others. But as soon as profile pictures were restored, 2,200 conversations incidentally ended.

"The goodness was gone, in fact, worse than gone. It was like we'd turned on the bright lights at the bar at midnight," wrote Rudder.

The second experiment examined the results of a poll that stated personality and looks were of equal value. The researchers decided to hide written information on the profiles of some users, then measured the number of people who would ignore those that didn't have text bios. The experiment showed users still sent messages to those with pictures only, and that text on profiles constituted less than 10 percent of their judgment.

"So, your picture is worth that fabled thousand words, but your actual words are worth...almost nothing," Rudder explained.

The last experiment evaluated the influence of "match percentage" in one's decision to send the first message. OKCupid manipulated the results of those with 30 match percentage to show as 90 percent instead; as predicted, users sent their first messages to those they were more compatible with, as dictated by the site.

It is uncertain whether any of the conversations turned into real dates, but the results concluded that looks are more important than personality, and people prefer to be with someone that they are most compatible.

Rudder defended the experiments, saying they played a significant role in improving the service of the website.

"OkCupid doesn't really know what it's doing. Neither does any other website... Experiments are how you sort all this out."