Twitter has 190 million users, generating 65 million tweets and more than 800,000 search queries per day. As a response to this growing user base and Twitter’s brand-friendly ad platform, the number of Inc 500 companies using Twitter has increased from 52 percent in 2009 to nearly 60 percent in 2010 and of those companies on Twitter, 81 percent considered the social network a successful marketing tool in 2010. Since its ad platform launched in April 2010, Twitter is expected to generate $150 million in revenue in 2011 and $250 in 2012, predicts eMarketer.

Twitter has become a magnet for brands seeking user engagement and has built an ad platform that accelerates these objectives. In times when marketing budgets are stretched, Twitter’s platform focuses on performance, brand engagement and might be just what businesses are looking for . Here are several reasons you might want to investigate Twitter’s emerging ad platform:

Twitter has three different types of “promoted” Tweets:

Pay-Per-Follower — The most attractive feature of Twitter’s ad platform is its promoted accounts. Often, brands want to build a sizable following very quickly and Twitter’s promoted accounts are an excellent, performance-based way to do it. Promoted accounts are cost-per-follower ads that target what users talk about and who they follow. For smaller companies with little brand recognition, this is a fantastic way of building a large following, in a short period of time.

Cost-Per-Click — These Tweets follow a similar structure as Google AdWords. Marketers bid on keywords that appear in Twitter search results and trending topics. Every time users click on a promoted Tweet, you pay n. Links can be directed to the brand Twitter page or content outside of Twitter’s gates. It is a very simple, straightforward and easy for digital marketers in the PPC game to wrap their brains around.

Promoted Trends — This is very much a traditional media buying option, where brands purchase a place on the trend pages for a day. As Twitter trends are on the homepage of Twitter, brands can get a lot of impressions and clicks from a single sponsorship. This option would be suitable for marketers familiar with traditional media buying.

Twitter’s ad platform can appeal to your traditional marketer with promoted trends, digital marketer familiar with the AdWords model and is taking advertising to the next step with cost-per-follower. Twitter’s ad platform is relatively new on the scene and it is difficult to determine the ROI, but those on the ground floor could certainly benefit from the minimal competition.