Suspicious survey

I received an email today from Acurian, asking me to take a "brief and confidential market research survey" to "assess the prevalence of specific types of cardiovascular and heart-related conditions." It made me a little suspicious. An email survey isn't exactly the best way to assess prevalence of such conditions. Meanwhile Acurian is in the business of recruiting patients for clinical trials.To entice people to participate there is the promise of a raffle for three prizes: $200, $100, and $50 for a whopping $350 in total. The first question asks for:

"Your E-mail... so that we may contact you if you are a $200, $100, or $50 raffle winner."

I decided to take the survey without providing my email address. I don't care about the raffle and I didn't want to attach my email address to my results.The survey asks whether I have certain heart conditions (e.g., heart failure, atrial fibrillation), what medications I take to treat the conditions, what procedures I've undergone, whether I've had a heart attack or stroke, and what might motivate me to participate in a clinical trial or prevent me from doing so.Then there are some specific demographic questions including zip code, age, income, insurance status and race.I filled everything in and then hit "Submit Survey." My survey was rejected because I didn't provide my email address. It made me wonder --are they really so worried I might miss out on the raffle? Or are they building their database of potential trial participants?My email address plus what I'd included in my survey plus a cursory search on Google would be enough to identify me and build a substantial file. There are no specifics given about a privacy policy or how the information will be used beyond the statement that the survey is confidential.I'm going to write to the the CEO and ask what is going on. Stay tuned.