Fortran (and COBOL) has traditionally designated different behaviour to different columns. A character in a specific column has a different meaning than if the same character is in a different column. A variable-width font in that situation is completely unmanageable.

Nowdays, both Fortran and COBOL has changed this stupid design and you are now allowed to indent any way you want. If only Python could grow up too...

The Intent system is what makes Android so powerful. If I have an application that wants to sent a twitter message, it can send an Intent with a request to do so. This Intent can be picked up by any of the applicaitons you have installed, so that the developer not only doesn't need to develop twitter functionality, the user can also choose to use whichever twitter application he wants, and it'll still integrate perfectly.

In case you were wondering, if more than one app is prepared to handle an Intent, the user gets an option to choose withich one should be used, and can store that as a default for the future.

Everything uses Intents, even basic functions such as sending an SMS, which is why alternate SMS applications works completely transparently. Another Intent is the one that displays the main "desktop". Again, no need to be limited to the default desktop application.

Just because no other mobile OS'es gets this right, doesn't mean that Android is wrong.