Interest in Pinterest is skyrocketing.

Launched a little more than two years ago, the social photo-sharing service has doubled its number of daily unique visitors to 4 million since January, according to new data from social media marketer Tamba. The site's core users are women, age 25 to 54, but the site is attracting the interest of men, who now make up 28 percent of new members compared with 20 percent in January.

More money is also being associated with the site, according to Tamba. The percentage of social media-driven revenue that comes from Pinterest has grown from 1 percent in the second quarter of 2011 to 17 percent in the second quarter of 2012. In that same time, Facebook has declined from 89 percent to 82 percent, and Twitter has plummeted to 1 percent from 10 percent.

In the wake of Facebook's acquisition of Instagram, those numbers make Pinterest ripe for buyers, as my colleague Rafe Needleman points out. "There's really only one startup that emerges as most Instagram-like: Pinterest," Needleman writes. "All the others are battling for position as distant followers."

Launched in March 2010, Pinterest has raised $27 million to peg it at a $200 million valuation -- $50 million shy of what Instagram raised to loft it to its pre-acquisition value of $500 million.

See Tamba's infographic below for more information about Pinterest users.