Snapple is competition for Coke in the category of “refreshing drinks”, but not competition in the category of “carbonated cola drinks”
However, as the social-cultural environment changes, the segment for carbonated cola drinks may decline as alternatives become known among other variations of beverages - as in the case of how ice tea became popular in the 1990’s.
When Blackberry first started selling smartphones it did not consider Apple a direct competitor in the beginning because Blackberry had BBM and other things which they thought made for a more attractive product.
As iPhone became more popular among MAC users, and then the general public, it was followed by thousands of developers making “apps”.
Unfortunately for R.I.M., most of the app developers only made an app which could be run on iPhone, or iPhones and Android, leaving Blackberry users without these particular opportunities.
So we can see that over time iPhone became a stronger competitor NOT only in a direct one-to-one context of product versus product, but also provided competition by virtue of the fact the iPhone became a more “useable” product because of the many 3rd party entities creating apps for the iPhone.