Technology equities have highly variable price to earnings rations because of the expectation of greater growth in the future. This expectation means investors are effectively speculating about the future growth of the company, rather than making decisions based on classic quantitative methods like you would apply to an older company in a better understood industry. Applying these methods ignores this dynamic and also buys into the myth of the quantitative analysis that's so appealing to mathematically minded geeks like ourselves.
I submit that the only thing posts like these really accomplish is letting the author stroke his or her by using big words and apparently clever concepts, while simultaneously making it clear that they're misunderstanding the market.
A smarter model for valuing tech companies would look at what their actual worth is, then separately factor in some kind of "bubble factor" or "irrational exuberance" factor that would price in the sentiment of people buying/selling the stock itself.
Twitter reminds me of AIM (AOL Instant Messenger). Back when AOL was a big deal, AIM was how you chatted with people and the network effects of that were incredibly huge. Everybody, every brand, everything was on AOL. Then, the landscape shifted and high speed internet made AOL irrelevant. However, AIM was still around and a lot of people used it for years after they quit AOL.
Twitter's big risk isn't the next few years where it's still hugely popular and integrated with media everywhere, the risk is in 5+ years when something else comes along. Will twitter have the staying power of Yahoo, Google, and Facebook, or will it be more of a AOL/MySpace kind of thing?
I really have no idea, but I wouldn't bet on Twitter for more than 5 years.
Honestly I'm surprised Twitter has filed so early, I'd have thought next year would be more likely. If I was investing (and I'm not), I'd mark it as a risky venture, the business is clearly changing at the moment but it's still certainly growing in the metrics and it has an increasingly large amount of visibility in mainstream media. They do seem to have a strategy though.
I think really the hard part in comparing these two companies are how users derive value from the two services.