From the AS Facebook page, looks like it was 139 passengers.
Two Alaska jets bump on tarmac at Sea-Tacby Alaska Airlines on Wednesday, October 27, 2010 at 10:03am
No injuries to passengers or crew; customers rebooked on spare jets
The right winglet of an Alaska Airlines 737 pushing back at Seattle-Tacoma International Airport bumped the left horizontal stabilizer of another Alaska aircraft parked nearby shortly after 7 this morning. There were no injuries onboard the aircraft pushing back, which carried 139 passengers and six crew members bound for Dallas-Fort Worth. No one was on the second aircraft, which was scheduled to fly to Minneapolis-St. Paul.
All passengers and crew on Flight 660 to Dallas were safely escorted back into the terminal. Both jets were taken out of service and are being inspected for damage. Passengers traveling to Dallas and those on flight 36 to Minneapolis-St. Paul are being re-accommodated using spare aircraft.