Source: http://appleinsider.com/articles/14/03/0...

Cooks' allusion to "23 companies over 16 months" was made two months into the second fiscal quarter of 2014, and the actual acquisition dates of some companies are not known with precision, making it difficult to pin down exactly which acquisitions Cook was including in his numbers. However, by any measure Apple has managed to buy up at least nine more companies than the investigative and curious media (including AppleInsider) has been able to identify.Cook made it clear in his comments to shareholders that Apple was not seeking to make the greatest number of acquisitions (or to pay the most money for them), but rather to make smart, strategic purchases whenever the circumstances arose. Unlike Yahoo, Microsoft, Google and Facebook, Apple rarely ever announces that it has acquired anything. Instead, it typically only selectively acknowledges acquisitions after they've been reported, regularly issuing the boilerplate statement, "Apple buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans."