Designing a logo is hard. No question. To have a logo that is recognizable in a split second is a major accomplishment.
So what happens when an established company wants to evolve the logo in an attempt to refresh or evolve it to appeal to a new demographic? It's a balancing act between preserving the existing equity and updating the look without making the logo unrecognizable to core customers.
Here's a great article showcasing good examples of bad logo evolutions.