If you are old enough on the web, you remember the time when Yahoo! supplanted Altavista as the search engine of choice. If you are less old, you remember the time when Google supplanted Yahoo! as the search engine of choice.
I remember both occurring, but never understood why it happened. Here is a former Yahoo! employee’s write up on why it happened.
Here is my favorite quote from the write up:
In technology, once you have bad programmers, you’re doomed. I can’t think of an instance where a company has sunk into technical mediocrity and recovered. Good programmers want to work with other good programmers. So once the quality of programmers at your company starts to drop, you enter a death spiral from which there is no recovery.