Apple stock closes above $550, breaks into positive territory for the year

Apple came into 2013 at $554 but slipped to $549 on Jan. 2, the first trading day of the year. Shares dipped as low as $392 in mid-April —  a trough nearly matched again in June, and one for which some analysts blamed opportunistic short sellers —  but have recovered steadily since the summer.

Cupertino again broke $500 in the days leading up the announcement of the flagship iPhone 5s and mid-range iPhone 5c, and has continued to climb on the back of strong sales of the handsets as well as the all-new iPad Air and second-generation iPad mini, which now comes equipped with a Retina display.

The company's stock resurgence has still not satisfied its most vocal investors, however.

Activist investor Carl Icahn —  who revealed a $2.5 billion position in August that has since swelled to over $4 billion —  continues to call for an increase in Apple's stock buyback program, which is already the largest such program in corporate history. Icahn has pressed the issue in person during meetings with Apple CEO Tim Cook, exchanges which are said to have been "a little testy."

Adding to the pressure from Wall Street is Greenlight Capital chairman David Einhorn, who earlier in the year famously sued Apple for keeping what he believed to be too much cash on hand. Though Einhorn dropped the lawsuit, he still believes Apple is not doing enough with its over $140 billion in cash, telling CNBC that he believes "More could be done that would unlock probably even more value, but it's not so bad at this point that I want to complain about it."

As of October, Apple's corporate cash hoard represented more than 10 percent of all non-financial corporate reserves in the United States.