This year I'll qualify for UA 1K, Delta PM, and SQ PPS. I'll also hold about half a dozen second tier cards which includes most US majors and all the alliances.
Previously, I used to fly Delta first and not pay attention to other airlines and only qualify for their elite programs by luck. When Delta stopped handing out SWU's for additional mileage I decided to go for more than one 1000,000 level. It was easy to move an extra block of mileage to get more SWU's froma nother carrier. I wonder why Delta didn't see that.