The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.By Ryan Fuhrmann NEW YORK ( StreetAuthority) -- It has yet to happen, but some day a public company could reach a total market capitalization of a trillion dollars. Think it can't happen? Consider that in this era of a global economy, where emerging nations such as China, India and Brazil will soon join the ranks of developed nations (and new emerging countries will rise), there is a chance for a certain class of elite companies to become even more dominant than ever before. But first, let's talk a little about market cap and why a trillion dollar market cap would be so astounding. Market cap is simply the number of shares outstanding of a stock multiplied by its current share price. These days, many companies, such as Pfizer ( PFE), JPMorgan Chase ( JPM) and BP ( BP), sport market caps in excess of $100 billion. Fewer still, are companies with market caps in the hundreds of billions -- General Electric ( GE) and IBM ( IBM) are good examples. Even fewer have what it takes to continue growing at the rates needed to reach a trillion-dollar market cap. But I've come up with three companies that just might do it.