I'm pretty sure that most cats don't really like being kissed on the head by humans, but if they at least usually put up with it, you probably are at least considered to be a tolerable assistant.
@lauren I suspect that they like being touched on the forehead in general, because they often rub it against objects and people (presumably as part of leaving their scent on them).
@robryk @lauren yep, sometimes a bit of forehead scritchin gets the 'oh yeah right there keep doing that' push