I really like Google approach to extending their applications beyond their core features and encouraging research and development by the masses.
I was just reading a post on the Official Gmail Blog: Gmail Greasemonkey API issue. They outline how they have updated Gmail Javascript to load in an iframe.
They talk about how this change may create some side effects in how some scripts work.
They fully embrace the fact that Greasemonkey is a widely adopted method of extending applications, including most of the core Google Platform Applications.
I just am really impressed how they allow and even work with the masses of hackers and coders out there, who are wanting to get the most out of applications they use.
This type of open research and development and social programming is great, and I feel it is one of the reasons why Google continues to stay at #1.
Kin Lane 