To answer your question simply, yes, investors believe it will be hugely profitable in the future. That's the only reason to invest in any company that doesn't

To answer your question simply, yes, investors believe it will be hugely profitable in the future. That's the only reason to invest in any company that doesn't make a profit today. It is not as unreasonable as you might think. Look at how fast Facebook's earnings are growing in the last 2-3 years. Investors hope Twitter can replicate this, even if it is at a smaller scale. Whether they are right or not is obviously up for debate, and you can take part in this debate by buying/selling/shorting Twitter in the stock market.