But when you can credit all DL (and AA and other airlines') flights to AS, the problem still remains that one could do the same MRs and credit to AS instead.
Seriously. This is the first year I hadn't contemplated that SEA-ATL-JNB RT to rack up some miles because it was ~$1100-$1400 because I'd hit 75K, but it'd be pretty easy to do still using your MP account, no?