Just wrote this on the Dec 2012 thread, but I'll add it here...
Just talked to a CM about getting a pin code. When I asked him what might up my chances for getting one, he said it was completely randomly generated by email. Registering at the WDW site, taking surveys, saving vacays, none of those things will up the chances. Totally random, which explains why people who've never done anything Disney-related have gotten one.
Also, the CM confirmed that the likely release date for Nov/Dec free DP will be late summer (July/Aug) but maybe even into September.
We went last December and the free dining was extended to us on August 3rd. We are going again this year on December 14-21st so I am holding my breath that we get that same email this August!!!