Since reaction to one of my editorials started this discussion, I guess it is time for me to chime in. While it is true that you do not have to answer "surveys" from pesky legal people (unless they are attached to a subpoena), the bigger picture to worry about is what they might do with the results of the survey without the participation of honest FTA owners.
All of this is a "fishing expedition" by DISH Network's legal staff in order to build a case to make a later argument that Free To Air receivers are primarily designed for theft of services such as theirs. Suppose that more than 50% of responders to such a survey answer it in manner that implies they are on the "dark side", having modified their equipment. DISH may manipulate the results of such surveys in such a manner that if you do not respond, they assume you are guilty of what is suggested. We don't know if such a survey is from telephone or mail responses, or what questions might be asked. But if they can compile statistics that suggest that more than 50% of receivers have been modified, some judge will be easily convinced to allow further legal processes that could eventually result in certain digital satellite equipment to be banned from further import or sale because over half of previous units were used in an illegal manner. An argument to claim that you may be using your equipment in a totally legal and legitimate manner could fall on deaf ears if such a determination is judged.
Hopefully things will not go this far, but it appears that their legal strategy is to sue somebody at the manufacturer level, in an attempt to recoup some of the costs necessary to convert their badly compromised security system to something that actually works. We do not want a legal precedent to go this direction, so think long and hard about ignoring an information request, and document how you answer such an inquiry. If you are being bothered by such a request, they already have your name and contact information. A barrage of truthful answers telling them that you are using your equipment solely for the reception of non-encrypted non-subscription services surely cannot help them get the 51% that they want in their argument, and would stop this legal angle in its tracks.