With as many community contributions to the MSDN library as half of the top contributors COMBINED, Thomas Lee has come to embody for us the reasons why we built this feature in the first place. Single-handedly, he's nearly created a 6th programming language for the library with all of his Powershell code samples. (In fact, that's his not-so-secret agenda: to motivate Microsoft to create Powershell samples at the same time as the C#, VB, and JScript ones...)
Community contributions (aka the Wiki) enables all of you to add all the code samples and real-world examples right into the library next to the official content.
Thomas just posted a mini-retrospective on why he's doing this and what he gets out of it. You've heard of the power of crowds, but I think this is a great example of the impact that just one person in that crowd can have.