Standard & Poor’s on Tuesday downgraded Google’s stock (NASDAQ: GOOG) to a “sell” from a “buy” in the wake of the search giant’s $12.5 billion acquisition Monday of Motorola Mobility. S&P lowered Google’s price target to $500 from $700.

That’s because in buying Motorola Mobility, Google acquired a low-margin device manufacturer with a huge payroll. In contrast, Google’s core business — online advertising revenue derived from its market-leading search engine — generates tremendous margins.

Well, it’s not like Motorola was going anywhere with their crappy Droids and Xooms. Android fans will keep enjoying their Samsung and HTC phones. Google will try to get revenge against Microsoft and Apple’s patent trove acquisition with Motorola’s 17,000 mobile tech patents. Android vendors are praising the deal—probably because they don’t want to pay any more licensing fees over patents.

MMI is up 66%, while NOK is up 25% and RIMM is up 16% with the great news.