I think gullability has to do with education and experience levels. For instance, there are plenty of folks who are not sure power conditioning will work for them and make an audible difference. Until they try it, that aspect of hifi-dom could be snake oil in their eyes. ANd even then, their personal experimentation may convince them it is, or it isn't!
Sure, fruity pebbles may be an obvious one, but for some folks many of the cable discussions and component and widget options available to us can be downright confusing.
Quick dump, back to my meeting....