It doesn't help that on my most recent flights, BA has text me the survey before I've even flown. Last Thursday for example I got the message through whilst sat in Galleries about an hour before departure. On my way back I got the message on my way to the airport. By the time I had landed in each case it was back to business and I'd forgotten about the messages until this thread. tried to reply now and it's too late. Which is a shame as I had excellent crews on both flights and would have happily filled in the surveys to that extent if I'd been prompted on landing. I would suggest this kind of error skews the overall results towards a negative because a customer who is upset and wants to complain will actively seek out a way to do this - probably more so than someone who was perfectly happy with the service.
If my bonus was affected by systems like this, I'd be annoyed.