Apple

Apple could see more than 600 million users by the end of 2013, up from 500 million currently, according to Morgan Stanley analyst Katy Hubert.

The 600 million figure assumes that 40 percent of Apple's device sales will be to new customers. If the forecast holds true, Apple stands to generate a healthy amount of revenue and free cash flow per account.

Following growth of an estimated 55 percent in 2012, Apple's current tally of 500 million users ranks second only to the number of people on Facebook. Each of those accounts spent on average $329 last year, leading to free cash flow of $95 per person, much higher than the free cash flow captured by such tech players as Facebook, Amazon, and eBay.

"Apple's advantage over other hardware platforms is its ecosystem, which creates 'stickiness' and opens new revenue streams," Huberty said in an investor note out today. "New services, like mobile payments, video, streaming music, or ad exchange, can help monetize Apple's user base. One of the opportunities is mobile payments, where Apple can leverage its large user base, secure platform, and acquired AuthenTec technology."