Twitter's efforts to generate ad revenue will kick into high gear this year and be quite successful, according to a new report. eMarketer estimates the company will earn $150 million in 2011, up more than 333 percent from the $45 million it may have earned in 2010. Obviously, that would represent a huge increase. Then eMarketer thinks Twitter will achieve a repeat performance of sorts in 2012, upping its ad revenue by about $100 million again to $250 million.