Would you/have you participated in scientific experiments?

Today, we had some scientists from a local university and some engineers from a tech company in our office. They were testing an exoskeleton type thing meant to help auto manufacturers be safer (e.g. fewer strain injuries). They were actually looking for volunteers to try it out. Everyone in the office was really excited to try it - both for the different-from-your-average-monday aspect, but also because it's cool to think that, in some small way, you're aiding in the search for knowledge that will help people some day. 

Have you ever participated in an experiment? Why did you do it, and what did you think?