With last years offer, I ended up going from silver to sg to wp in one - not-so-foul swoop. I currently have a choice of 3 different coloured q-cards to use when flying
Ditto - last year's double SC offer combined with three (long and tiring!) days of flying took me straight from almost-PS to almost-WP (I left myself ~100 SC short as I already had flights booked in the weeks following my SC run to make the extra ~100 SCs). I would have made PS and
might have made SG without the offer, but definitely wouldn't have made WP - not to mention that SC-running got me to WP in July last year, ~8 months earlier than I would have made SG (if I even made it at all).
I still feel a bit guilty sometimes - that I "gamed" the system - but I guess at the end of the day if QF chose to offer me a double SC offer (and JASAs!) then I'm within my rights to use it however I see fit.
The flip side of the coin is that now I have attained the status I am more likely to travel the extra to retain it. In other words the promotions have won QA extra business from me. not to mention those that I fly with and talk to.
This is a good point, and definitely applies to me also.
Apart from the points and $$ I burned / spent attaining status, I will almost certainly burn / spend more in the future to retain status. Plus, I'm booking QF flights far more often than previously. I used to spread my domestic travel around a bit whereas now it's all QF, and previously I would almost never travel QF int whereas now I have a preference for QF assuming the fare / convenience difference isn't massive.
Then there's also the "people I talk to" benefit for QF, as you mentioned. As one personal example, since seeing the benefits I get as a QF WP, the owner of the company I work for is directing his 2 / 3 annual long-haul J trips to QF to attain status of his own rather than spreading them around amongst different airlines. Next up is teaching him the benefits of JASAs
Does this make having assisted me to WP "worth it" for QF? I can't say for certain but I reckon the answer is almost definitely yes: I cost them a bit more due to having lounge access, extra baggage, access to premium desk, etc, but I doubt these minor extra costs outweigh the extra revenue I'm generating for them both directly and indirectly due to attaining WP.