I enjoy doing surveys, so I've signed up for the 'advisory board' (aka people we can trick into doing our research for free) for our phone company, cell phone company, energy providers, etc.

I just finished a survey which included the following question: "do you use a mobile phone?" The possible answers were: "yes, no or I don't know."

I don't know?

First of all, wouldn't you know it if you used a mobile phone? And second...if someone really doesn't know, do you want them helping to shape your company's future products by participating in your research?

Maybe that's the verification question to ensure that automated programs aren't completing the survey or something...