Many people want to use downloaded extensions in their own way. As for me most of the extensions require me to correct Yii::import() instructions inside their source code. All these extensions are directory dependent. To avoid the situation described above, I suggest to implement pseudo-anonymous aliases:
If you're working a lot with extensions you often stumble upon problems, when you want to include them into your custom web application, like hardcoded or absolute path aliases or classes extended from core application components, which implement addiditonal features.