We reccomend using a contest as a way to learn about your visitor. People are more likely to tell you information in exchange for the opportunity to win something. It is best to keep your questions to five or ten, any more then that an your customers are likely to lose interest and not complete the survey or enter your contest. As we all know Spam can actually cause more damage to your company then positive effect. Privacy policies are dictating that individuals should be able to opt-in to a mailing list.
Contests are and excellent way to ask people to opt-in.
At the same time you are collecting information, you can collect their email and get permission to add them to your list. This list will obviously be people who are interested in your products. Most Contests take at least 3 months to get rolling. Don't waste promotional efforts by not running your contest for a long enough period of time. The results from your Survey.