For those who won't take the time to read it end to end, I'll summarize it.
Many high growth companies can be profitable. They have enough revenue to cover their essential costs and could easily decide to show a profitable income statement. But they don't make that choice. Instead they invest heavily in the business with the expectations that those investments will produce more revenue (by hiring salespeople), or additional products (by hiring engineers and product managers), or additional geographies (by hiring an international team), or any number of other value enhancing aspects of the business. The result of that decision is that the business loses money or simply breaks even (I prefer the latter approach).
There was a discussion of profits (or the lack of them) in the comments to the IPO Market blog post I wrote last week. A number of commenters pointed out that many web companies lack profits. I don't think that is actually true (certainly not for many that have gone public), but it is true that most, if not all, web companies are not optimizing for profits this year or next year. They are optimizing for the ultimate size of their businesss and the total amount of cash flow they can ultimately expect to generate when the business gets to maturity.
This is tricky stuff. If you are going to take all of your potential profits and reinvest them in the businesss in search of higher growth and greater profits in the future, you had better be right about those investments. And it is often hard for investors to see how those investments are going to pay off, so at times you can be penalized for making those choices. Right now the public markets seem to be paying companies more for long term growth than for near term profits, so it seems that public market investors (and VCs) are aligned in this respect. But that is not always the case. Markets are fickle. But the best entrepreneurs are focused on the long term vision and will invest in their businesses without paying too much mind to what investors want at any point in time.