I used to do marketing research as a teenager (it was my first official job after babysitting my entire small town as a kid!). =) It paid a ton, the hours worked for after school, and it got me into a "city" from my tiny town.
To this day, no matter how busy I am, I will _always_ (without fail) complete a survey. Doesn't matter what product it's for. I remember being sixteen and trying to get those "completes" (a finished survey) on the phone in order to meet quota at the end of the night/week (I still have nightmares about it, on occasion, and I'm 38 years old!), so I know how it is to be that person on the other end of the phone.
I'm still tickled every time the survey has gone on for about fifteen minutes and you can just hear the nerves in the back of the interviewer's throat. We used to do a 45 minute long survey (it was for the company Schweppes) and I remember the twenty minute itch, that period where you were so close to the end and you just KNEW the person was about to hang up on you. It wasn't like they could be blamed, but you wanted to get that complete so badly... I always tell the people who call not to worry, I'm going to stay with them no matter what. The sigh of relief is even better than the sound of their nerves! =D