I suspect those being banned have either just been clicking randomly, or have been too distracted to notice things like: "Which of the following has four legs? Car, Dog, Comb", or "Choose TSB from the following options, no matter which you would normally pick... (Next line, in bold) Which bank would you consider as your main bank?".

I've only sat through five surveys so far, but each of them has had a little test around 2/3rds of the way through just to make sure you're paying attention.

(I did fail to qualify for two of them. One included a question along the lines of "Do you live in the country you hold residency in", which when I said "yes" was an instant decline. The other one was steering me to using websites which I don't have any interest in, so again an instant decline when I said as much!)