As for IBM, its market cap is quite close to Microsoft, so I think they did reasonably well (they could have done even better if they've bet on software earlier, but that doesn't mean they should necessarily "bet outside their walls"). Also, the fact that they invested everything they had on an "open" platform (the PC architecture) is kind of an agreement to what you said they should have done... No?
As for Twitter, I find it funny that people see it as such a revolution. I mean, it's just a little social network with a very limited scope and features... I don't jmagine it revolutionizing more than it already does (it's a great outlet for the media, celebrities and breaking news, but I don't think it's sooo much more)... Or is it? :)
I think the limited scope of Twitter is/was one of the strengths of the platform. Unlike the various walled gardens growing out of every corner, trying to be everything to everyone, Twitter was very effective for a specific style of communication.
They should monetize access to their API with some sort of tiered data-volume scheme. Under a certain amount per month = free, over that, begins to incur charges. They could also allow anyone to develop against it, with a license which acknowledges a cut of revenue over a certain amount.
IBM's market cap is now what MS' is for a different reason. When it comes to the PC war and the bets that were made, IBM lost. The lost so bad in fact, they had to completely scrap their entire PC business by selling it off.
IBM now makes most of its money through consulting, software services, and enterprise hardware and software.
As for Twitter, I find it funny that people see it as such a revolution. I mean, it's just a little social network with a very limited scope and features... I don't jmagine it revolutionizing more than it already does (it's a great outlet for the media, celebrities and breaking news, but I don't think it's sooo much more)... Or is it? :)