Who Would We Miss? Microsoft, Yes. Apple? Sort Of. RIM, Definitely.
IBM: Widespread Difficulties.
Although I'm sure the disappearance of IBM would be a big problem all over the world, it's hard to put a finger on exactly where. Most of us don't notice IBM anymore, but it's still all over the place in new tech and old.
Believe it or not there are still lots of companies, banks for example, using mainframes for very important programs. They work well; why mess with success?
IBM has an enormous IT services business that would be missed. And it does still sell a lot of servers.