By rolling my trusty over the names of each Straight Dope Forum, I have collected the following information:
**Forum ID**
ATMB 2
CCC 1
CMA 6
GQ 3
GD 7
IMHO 12
MPSIMS 4
Pit 5
WTF? 
[ul][li]What happened to 8, 9, 10 and 11?[/li][*]Why are they out of order (oooh! I just figured that one out!)[/ul]
Someone was just asking about this the other day, but with a non-intuitive thread title. I’ll see if I can dig it up. To answer the first question, the missing fora are the Archives. Back in UBB, the mods had the option to preserve a thread in perpetuity by moving it to the Archive version of the forum, so that no other posts could sully it, and it would always stay near the top of the list. That’s no longer supported well in vB, so those fora are now just sort of abandoned. They have the numbers you mentioned, so when IMHO was created, it took the next available number.
Your second question is actually much simpler. The fora are numbered in the order that they were created, but they’re listed in alphabetical order. It’s pure coincidence that this puts them in an order that seems to make sense based on content.
Am I supposed to know who Hank Hill is?
Hank Hill is the character in a USA network television animated programme.