Poupada predicts that Pinterest is in a pre-evolutionary stage, just as "Facebook was once considered for college students." The bookmarking site may attract a more balanced group of users once it tweaks its branding, he says.

"There will always be places to be gender-specific," he said. "There will always be the (male) equivalent of Pinterest. But the beauty of the Web is you can never stop anyone else from joining. The medium doesn't allow it."