If the ongoing social networking revolution has you scratching your head and asking, “Why do people spend time on this?” and “How can my company benefit from the social network revolution?” you’ve got a lot in common with Harvard Business School professor Mikolaj Jan Piskorski.

Only difference: Piskorski has spent years studying users of online social networks (SN) and has developed surprising findings about the needs that they fulfill, how men and women use these services differently, and how Twitter—the newest kid on the block—is sharply different from forerunners such as Facebook and MySpace. He has also applied many of the insights to help companies develop strategies for leveraging these various online entities for profit.

…”People just love to look at pictures,” says Piskorski. “That’s the killer app of all online social networks. Seventy percent of all actions are related to viewing pictures or viewing other people’s profiles.”

Why the popularity of photos? Piskorski hypothesizes that people who post pictures of themselves can show they are having fun and are popular without having to boast.

Another draw of photos (and of SN sites in general) is that they enable a form of voyeurism. In real life there is a strong norm against prying into other people’s lives. But online enables “a very delicate way for me to pry into your life without really prying,” the researcher says. “Harvard undergrads do it all the time. They know all about each other before they meet face to face. ‘Oh, you’re that guy that did that internship in D.C. last summer.’ “

Piskorski has also found deep gender differences in the use of sites. The biggest usage categories are men looking at women they don’t know, followed by men looking at women they do know. Women look at other women they know. Overall, women receive two-thirds of all page views.

“This was a very big surprise: A lot of guys in relationships are looking at women they don’t know,” says Piskorski. “It’s an easy way to see if anyone might be a better match.” Again, online networks act as cover.

Piskorski says these findings do not hold for one network: Twitter.

Looking at who uses Twitter, which restricts users to 140-character messages, Piskorski and student-researcher Bill Heil (HBS MBA ’09) found that 90 percent of Twitter posts were created by only 10 percent of users. This was not surprising, he says, because the technology uses words without photos to communicate.

“Only the people who are willing to put themselves out there publicly in words to people who they may not know will use Twitter. Some people will find this incredibly appealing, others will find this too scary.”

Read the whole article from Harvard Business School Working Knowledge.