By 2012, says Gartner, 20 percent of all businesses will turn their backs on their own data centers and move to the cloud. For cloud computing advocates, and indirectly Green IT geeks, it’s an encouraging forecast. However, it’s one that’s a tad (insanely?) overoptimistic to our own Infrastructure curator Derrick Harris.Why? There are a couple of reasons, but I’ll give you one big hint: Google and China.