Anyone have a reason not to add this config option?

I don't know what the policy is on adding configuration options to
rails/activerecord, but I think this would be a useful performance
option:

http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1185-old-single-query-includes-should-be-globally-disableable

I've replied in the ticket. I don't think this is a good idea.