Evolution of Logos and the Popularity in Altering Them

I think a popular trend lately in the graphic arts world is the evolution of and re-do of logo designs. Rather than completely change a logo however, companies/corporations recognize that their original logo has built a foundation of trust and a 2-way relationship with its consumers. In order to prevent cutting off this connection, these corporations have invested a lot of time and money into altering their logos slightly, in order to improve them. Here are some examples I found: Nike for instance, used this icon for a long time; it has the swoosh and the nike text. Although it was not the first logo that it had, it still used the same elements as the first logo. The logo that came out after simply placed a square around the Nike text and swoosh sign. The current official logo however, is now JUST the swoosh sign. They no longer need to write "Nike" because they have established themselves in the world as an entity, an idea, etc. When anyone sees the swoosh sign, he/she can immediately recognize Nike. Apple is another example, (http://www.instantshift.com) Apple, as I remember it in my 90's childhood was the rainbow-colored apple. It was cute then, but as we went into our new millenium, the rainbow color became "too 90s" and the Apple logo evolved into a sleek white apple. This also matched the Macbooks that Apple became famous and popular for. It also portrayed Apple as a more technologically-advanced, futuristic company. If these logos had not advanced like the rest of our world in a more futuristic way and made a name for themselves, they probably would not appeal to the people and be out of business by now.