Sales of IP addresses have been common place since about the late 90's or so. I had a class C block for 15 years and had offers many times, but I turned my block into ARIN about 1.5 years ago (yes, it was assigned to me for personal use before the Internet was commercialized, they used to do this). Microsoft has done nothing different from what many other companies have been doing for years. I bet Google has bought IP addresses from companies and individuals. This story only exists because it's "Microsoft".