Re: Tim Worstal
P/e is based on profits ('net earnings' in the chart you link to). Revenue is the sum total of money coming in, and so the revenue number doesn't automatically tell you how much profit a company are earning.
Price to revenue is a metric which is principally used by dot com hucksters to try to hide the fact that the firms they're pushing are usually drowning in red ink. If you tried to measure any normal company using it then you'd find a ratio in the low single digits (Apple's is a bit over 3, for example).
Facebook aren't drowning in red ink, and actually do make a profit. It's just not anything like big enough or growing anything like fast enough to warrant the valuation it has.
They're far from the scariest company to be invested in though. Linkedin's p/e and p/r ratios are absurd, and Salesforce are valued at $19Bn despite running at a loss and having annual revenue just over $2Bn.
The only reason not to short those two is that if the sheep keep plowing in (on the back of glowing analyst recommendations), then you might be bankrupted before someone spots that the emperor has no clothes.