I don't think Microsoft's response to the web is comparable to their failures in mobile. billg's "Internet Tidal Wave" memo went out in 1995, long before the web had become ubiquitous. They still had plenty of time to (legally or otherwise!) ride the .com tidal wave to dominant marketshare and huge profitability.

A similar memo would have done the most good in 2005, when it was becoming clear that we'd soon all have access to pretty decent wireless networks and high performance pocket computers, but also clear that WinCE and the PocketPC were lousy ways to take advantage of those facts.