Facebook shares continue to plummet: They've now dropped more than 20% from their $38 IPO price, falling below $30 today to their lowest point yet, reports Reuters. At about 12:45pm EDT they were trading at $29.44. But among tech stocks, $30 per share still gives it a comparatively "generous" valuation, notes Dan Gallagher at MarketWatch: The site is trading at about 55 times its estimated earnings for this fiscal year. Google, on the other hand, trades at about 14 times its estimated earnings, and Apple, IBM, and Microsoft are in the same ballpark. But he notes that higher valuations seem more common among social sites: Groupon trades at some 64 times its estimated earnings, while LinkedIn is trading at a hefty 145 times its estimated earnings.