While I agree with Darren's sentiments generally, I have to argue with this:
Originally Posted by Darren
If I have a first class fare basis, and fly coach on a one-class plane, I will get coach miles irrespective of the fact that my fare basis is F or A or whatever.
That has never been my experience - I regularly fly on UAX services connecting from longhaul biz and always get my double miles, as the fare basis on the UAX segment is biz also. It may vary from carrier to carrier, and from FFP to FFP, but I've never come across this.