The only time I've heard of such incidences when people have been bumped off First Class in HKG, are mostly on Dragonair.. and that was when Mr and Mrs Tung Chee Wah are travelling!
BAloyal, had you refused to fly that day in Business Class abeit downgraded, you may have been able to demand more from CX but you chose to be taken to your destination that day. From personal experience and as a Diamond member, people in F class rarely check in 2 hours prior to departure and it just seems strange that when you did that 'all 8 people have already checked in'. It could have been a codeshare problem with the seats with SAA and both airlines double booked. But then again, I have never heard that of F being overbooked. J, Y yes. But never F.