Nearly since it’s inception Twitter has been attempting to find new ways to generate revenue and now thanks to their “Promoted” products a new study suggests that the company’s revenues will grow from $45 million in 2010 to nearly $400 million by 2013.

According to tracking firm eMarketer Twitter in 2011 is on pace to earn $139.5 million, a 210% incrase over last years numbers.

According to Debra Aho Williamson, principal analyst at eMarketer:

“Since their debut in April 2010, Twitter’s Promoted Products have proven successful in the U.S.,” while she adds “Marketers have shown solid engagement rates with Twitter advertising — in some cases better than those on Facebook — despite Twitter’s relatively smaller audience.”

With a user base that currently sits at 100 million active users the estimated revenue stream growth from Twitter could increase over the $400 million estimate if Twitter finds new ways to engage users and grow their base. In comparison Facebook current serves more than 800 million users worldwide.

What may be even more impressive about Twitters massive growth is the simple fact that most of their revenue and reach still comes from the U.S. market where they receive 96% of their overall ad revenue. Twitter plans to expand on those revenues with their first foreign office opening this month in the UK.

EMarketer predicts that by 2013 U.S. revenue will continue to climb but only equal 88% of the company’s overall revenue base.

Do you think Twitter can continue to expand at such quick levels in terms of business profitability or will their business model run stagnant at some point in the near future?