Mark Zuckerberg, CEO and co-founder of Facebook, has fired shots at Apple in his apparent disagreement with statements made by Apple CEO Tim Cook.

Cook said that free services that are supported by advertisements, such as Facebook, turn their users into products.

"A frustration I have is that a lot of people increasingly seem to equate an advertising business model with somehow being out of alignment with your customers," Zuckerberg told Time in the article "Inside Facebook's Plan to Wire the World."

"It's the most ridiculous concept. What, you think because you're paying Apple that you're somehow in alignment with them? If you were in alignment with them, then they'd make their products a lot cheaper!" Zuckerberg exclaimed.

In an open letter that was posted on the Privacy page of Apple, Cook said that in free online services, users are not the customers, but rather, the product. The letter was a component of the response of Apple in addressing concerns on privacy within their devices, after a massive hack that was able to extract several nude pictures of celebrities through iCloud accounts.

The Privacy page of Apple also looks to show how the company handles the data of its users. Except for iAd, Apple said that it is not interested in diving into the advertising business, with a business model for the company built around such an idea.

The argument between free services and paid services between companies and advocates for consumer privacy has been going on for years. Companies that offer free online services, such as Facebook, Google and Yahoo!, rely mostly on advertising revenue for their profits. In exchange for the free services, however, users are exposed to targeted ads based on the information gathered from them as they use the free service.

In the letter on Apple's Privacy page, Cook added that the company is focused on creating great products to sell to users, not building up user profiles with information retrieved from data storage systems and messages that can be bought by advertisers.

However, the argument for free, ad-supported services is that these services provide the most benefits to customers, with the revenue generated from advertisements allowing the companies to further develop and maintain the services.

The argument between free services and paid services will likely not end any time soon. While Zuckerberg criticizes the high price of Apple products and Cook calls out advertising-based business models, such as Facebook's, only one thing is sure. Between free services and paid services, both are working pretty well for Facebook and Apple.