I do mileage runs one a year on a few different airlines and have a lot of fun plus get all my reading done! To each his own, I guess.

I'm a United Global Service (which is based on spend, not miles, ~$80K/year gets you that) from business travel that's paid for by my clients, but for other airlines (AA) if I'm on the border of making "status" I will do a mileage run if I can.