For example, Apple. Why aren't the software and hardware divisions separated, at a minimum? Furthermore, I might wonder, why couldn't iPhone, iPad, Mac, Audio Accessories etc. be separate companies? Sure, you'd lose a ton of the integration that makes it special... but I wonder sometimes if the world would be a better place. Same for Microsoft: Why can't Windows, Office, Azure, Xbox, all be separate companies? If Windows was an independent company I think it would probably be way healthier for Windows at this point (less Microsoft bloat)...
I feel (just feel) that publicly-traded companies should be forced to pick a market segment and stick to it, and any other businesses that get too large (say, $1B revenue) must be broken off.