If you want to get people talking, ask them about themselves. [We asked] “What’s changed for the better since you started using Basecamp?” and, wow, impact came streaming in. Nearly 4000 people responded in just a matter of days — making it one of our most successful surveys ever.
This was also the case in my work at Google. When we asked questions like "What is your favorite feature of Google Play Music" or "What would you change?" the results weren't anywhere as insightful as when we asked about how people's lives were changed as a result of using our products.