Pinterest announced through their blog:
“We’re really excited to have the capacity to offer Pinterest to more people and if you’re a Pinner with friends who’ve been waiting on the sidelines, we hope you’ll let them know. Happy pinning to everyone!”
After the announcement, anyone can now register to their site using your twitter, facebook or an email account.
Pinterest hits 10 million unique US visitors way back last February and continued to grow up. A clear sign that their invitation to join style of registration would give way sooner to increase their users more.