...when doing P/E analysis, it's important that a company have (E)arnings. Not to be confused with revenue. Companies running at a loss don't.
An example of a publicly-traded company that has substantial revenue that isn't making money is Amazon.com (NASDAQ: AMZN). Their per-share data for the trailing twelve months: $8.15 sales, -$3.75 earnings, -$3.49 book value. That means Amazon is spending money faster than they make it. Therefore, there's a "N/A" next to the P/E ratio.
Amazon's debt is probably junk status. I believe that accounting practices benefits them concerning some of their investments (they hold equity stakes in many of their partners). One of the unusual features of Amazon's financials is their negative book value.
Contrast Amazon.com with Morgan Stanley (MWD), IBM, Chevron (CHV), or Ford (F). The latter four actually make money and pay their shareholders dividends and only MWD did not outperform the S&P 500 in the last twelve months.
