http://msdn.microsoft.com/en-us/devlabs/ee794896.aspx
In basis, Observable is the "other side" of Enumerable. While
Enumerable is consuming a sequence, Observable is producing. I heard
the presentation of Bart de Smet of this yesterday at the DevDays in
The Hague. Fascinating stuff. More info:
This is not a pattern that I would use in base2. Anyone want to convince
me otherwise? There is nothing to stop you adding your own Observable
module.
-dean