Pinterest just received a valuation of $3.8 billion. It is now one of the most valuable privately held Internet companies. It has also proven a very strong appeal to women.

Last May, the company was valued at $1.5 billion. After securing a $225 million in equity funding this week, their valuation has soared. And Pinterest hasn't really proven that it can actually make money yet.

CEO Ben Silbermann unveiled a strategy to bring in revenue through a "promoted pins" advertising program, which may have been impressive enough for it to land the funding.

[NBC News]