The 640 K Barrier
I attended a talk by Bill Gates several years back, where he stated that when IBM was developing the PC, he tried to convince them to base it on the MC68000, and that their decision to go with the 8088 set personal computing back a decade.  As the article points out, though, there were a ton of 68000 machines that ultimately got left in the dust by the PC, so I wonder how it would have really turned out.