Icahn tweets. Billionaire investor Carl Ichan, who tweeted last week that he had bought a "large position" in Apple, tweeted again this week that he's planning on having dinner in September with Apple CEO Tim Cook. "Tim believes in buyback and is doing one. What will be discussed is magnitude," Icahn said. If you haven't been following along, Icahn said last week that Apple's shares could be trading at $700 — and the company should use debt to buy back more shares. "Apple has the ability to do a $150 billion buyback now by borrowing funds at 3 percent." So is a bigger buyback coming? All I can tell you is that Apple shares were trading at $467.36 a share the day before Ichan announced his Apple stake. They closed yesterday at $501.02, a 7.2 percent gain. While that's still a ways off from $700, the shares are heading in the right direction. E-book saga continues.