I have a hard time understanding precisely what gives these companies such high perceived values. In the end I have to believe people are measuring the value b

I have a hard time understanding precisely what gives these companies such high perceived values. In the end I have to believe people are measuring the value based almost exclusively on the website's "traction". Frankly, I think "traction" is an outdated metric (especially when it comes to the web). I almost feel like I have to remind folks here (who are arguing against the premise that we're in the middle of a period of extraordinarily excessive valuations) that the web provides an almost frictionless environment to change. If tomorrow someone launches a better LinkedIn, there is ZERO reason I can't switch over (or use both) that same day). In tomorrow's world I see individual engineers (or surely teams of less than 10) will have the capacity to build a product better than LinkedIn, at and beyond the scale of LinkedIn, in their garage (thanks to the cloud). With little to no investment. In the future (by my estimation the not-too-distant future) $20+ billion for a resume website will be unconscionable (if it isn't already).