Pinterest, the virtual pinboard, has seen phenomenal growth in its short life. With a December 2009 launch date, the social photo-sharing site has reached 10 million unique views a month, more quickly than any other social media site.

This infographic shows the Pinterest's tremendous growth. With only 16 employees, the site attracts two million Facebook users every day, and 97% of the site's users are women.

The start-up does have a few challenges. Copyright complaints are rolling in, with photographers claiming that their images are used without their permission. Pinterest does have a process for reporting infringements, but when called a few days ago, the voice mailbox was full.

On its Pin Etiquette page, Pinterest warns users to "Avoid Self Promotion":

"Pinterest is designed to curate and share things you love. If there is a photo or project you're proud of, pin away! However, try not to use Pinterest purely as a tool for self-promotion."

This statement may restrict how companies can reasonably use the site for sales, but Pinterest still offers a big boon to retailers, who benefit from peer-to-peer promotion of their products. Mashable's compilation of 15 of the Most Popular Pictures on Pinterest shows a variety of images: hands, scenes, food, metallic nails, and more. Pinterest also offers views based on specific interests, such as planning a wedding or decorating a house. Clearly, the categories lend themselves to consumer purchases.

To sign up, users "Request an Invite" and receive this email:

"Hi!

"Thanks for joining the Pinterest waiting list. We'll be sure to send you an invite soon.

"In the meantime, you can follow us on Twitter. You can also explore a few pins.

"We're excited to get you pinning soon!

" - Ben and the Pinterest Team

According to Squidoo, all users likely get this email a couple of days later:

"You're in!

"I'm excited to invite you to join Pinterest, a social catalog. I can't wait to have you join our little community."

Discussion Starters:

• Do you think Pinterest could be "the next Facebook," as some suggest? Why or why not?
• Why do you think Pinterest attracts so many more women than men? 
• How do you assess Pinterest's strategy for people to "request an invitation"? Is it effective?