First of all, this is not a corporate raid - Icahn cannot force a decision to be made with the small stake he holds in Apple. He can have lunch with Tim Cook, and Mr Cook can still say 'no'. He can try to enter into a proxy war, but that will take ages, and I doubt he is willing to do that in the case of Apple.
Second, people here comment on the fact that Icahn does not care about the real business of the company. Perhaps. The argument runs that none of the companies he has invested in during the past have benefited from his investments and that he is a parasite leeching funds off the company to make a quick gain. That may be true to some extent. However, corporate raiders do not take over (or invest in) companies where the management is doing a perfect job - typically, they only invest in companies where management is doing a subpar job and there are gains to be made from the time and money invested. Those gains have to be sufficient enough to warrant the huge investments and time spent, so that means the management must truly be doing something inefficient.
This whole activity is simply a form of correction, where market participants monitor the management and take action if capital can be deployed more efficiently somewhere else. Without knowing that much about apple's business, it seems that Apple can return at least 50 billion in cash to investors and still have a sufficient cushion to invest in R&D and save for a rainy day. Perhaps the investors would prefer to invest that 50 billion in biotech, or semiconductors, or even cereal companies. As owners of the company they have certain rights to demand the cash back.
Well said. You don't have to be a fan of Carl Icahn to agree with his assessment that Apple has kept a lot of investor value off the table.