Here's my attempt to clarify the situation. From best practice to worst.
Best: First climber climbs route, puts draws on anchor, lowers from draws. Subsequent top-ropers climb with rope running through draws at anchor, subsequent leaders lower from the draws the first leader put up. Last climber (leader or seconder) cleans anchor, threads anchor rings and abseils from rope running directly through anchor. The only wear the anchor rings get is when the last climber gets to the bottom and pulls the rope i.e an un-weighted rope sliding through through them - pretty minimal.
This is the absolute optimal situation, you can't get any better than this unless you walk off. I'm sure anyone who's installed anchor bolts wishes more people would do this.
Middle: First climber puts draws on anchor. Subsequent top ropers and leaders lower from those draws. The last climber re-threads anchor and is lowered with the rope running directly through the anchor rings. The wear on the anchor is that of the weighted roped running through it ONCE.
This seems to be the accepted middle ground for cleaning a climb at the areas i climb at (Blueys mostly).
Worst: First climber gets to top and threads rope through anchor. All subsequent top-ropers are belayed with the rope running through the anchor rings directly. If there are 3 top-ropers, the anchor gets three times the wear.
To Linze and anyone else who seems to be missing the point. This is pure climbing douche-baggery. Don't ever do it. If you do and you get yelled at, you deserve it 100%. Don't go crying to the forum complaining how rude the Sheriff is, he was right.