Dam friction-less sharing and the company is toast Open ... and Shut No sooner did Facebook file its S-1 in preparation for an IPO than speculation kicked into high gear on how Facebook could possibly sustain its $75bn to $100bn valuation. After all, despite its hugely impressive revenue and profit numbers, key components of its revenue model – like advertising revenue – are decelerating. So should we expect Facebook to impose a paywall on some or all of its users, as MyLife.com chief executive Jeff Tinsley suggests it could?…