NEW YORK ( TheStreet) -- Amazon ( AMZN), Google ( GOOG) and even Facebook ( FB) have far different business models from when they each went public, and those considering the shares of Twitter should expect the same as the micro-blogging site looks to sell $1 billion in stock to public investors. Twitter's IPO documents, released late on Thursday, paint the picture of a fast-growing media powerhouse that sits at the confluence of news and advertising. While the San Francisco-based company now boasts annual revenue that is likely to exceed $500 million this year, cash flow and profits on a measure of adjusted earnings before interest, taxes, depreciation and amortization (EBITDA), Twitter's business model nevertheless faces tremendous uncertainty as a stock listing looms. The company generates 87% of its revenue from advertising on its network and, in particular, three sources: Promoted Tweets, Promoted Accounts and Promoted Trends. Advertisers are clearly interested in the platform. Twitter said in its IPO filing that its advertising sales have grown to $221 million in the first six months of this year from just over $7 million for all of 2010. Such advertising sales may grow significantly in coming years, helping Twitter to scale to a point of profitability as Google, Facebook and LinkedIn ( LNKD) have all done since their respective IPO's. Still, potential Twitter investors shouldn't just vet the company's IPO documents for growth rates and a picture of its current financial state. They should also think about how and where Twitter will evolve in coming years.