In spite of today's rally, Facebook (FB -5.6%) is falling to new post-IPO lows in early trading, and is once more taking related names down with it. ZNGA -3.9%. SVVC -1.6%. GSVC -2.3%. Investor unease with Facebook's reported plans to become a smartphone vendor could be playing a role, but the company's still-high valuation is a more likely culprit.