Ah, can you say "OS/2"?
IBM made OS/2 run Windows 3.x apps natively under OS/2 2.x in the early-to-mid 1990's. Nobody wrote OS/2 apps, since Windows apps ran just fine under OS/2. It's this very case that is probably prompting many people to warn about running Windows apps too conveniently.
The huge difference here, though, is that IBM never wrote any OS/2 software--not consumer software, in any case.
Apple, on the other hand, makes most of the software that users have on...