Bloodless Coup

Oy! Don't they know that the more questions you ask, the less accurate answers tend to become?

Which is why people shouldn't use the MMPI?

Depending on what the survey is after, more questions don't necessarily mean less accuracy, especially if they are measuring the same concept with multiple questions. They are, in fact, building in accuracy measures.

You get more data points, but as attention and motivation fade each data point becomes less accurate, like unfocusing a camera. The MMPI is a great example.

Heaven forfend we consider the costs of a long survey against the benefits of screening out unreliable information.

TL:DR