Hmmm, lets see, this year -
USAirways - approx 40,000
Delta - approx 20,000
AA - approx 15,000
Continental - only 5,000
United - approx 13,500
NW - approx. 10,000
AirTran - I don't collect from them but have flown about 1500 miles with them this year
Midway - same as AirTran but only about 1,000 miles
Midwest Express - same as AirTran & Midway but only 500 miles.
My NW & United miles are being donated to charity this holiday season, as I no longer fly them (my employer's edict, not mine!). Haven't flown Southwest yet, but they are on our "approved" carrier list, so I believe I'll be collecting from them next year.
I think that's about it!!!!