It was a survey Stardock authorised. Nothing to worry about, no fraud involved at all. The survey period is now over.
Here's the text from the email I was sent:
Dear Stardock Customer:
Your feedback is the most valuable tool we have. Please take a moment to answer a few questions about our products in a brief survey.
Stardock appreciates your time and comments. Your answers will help us evaluate ourselves and learn more about the things that our customers are looking for.
At the end of the survey you will receive a coupon code for 20% off any product over $8.00. Offer is not valid with any other offer. Coupon expires on September 30, 2008.