Doing a survey?

During our feasibility study days in college, we were tasked to do some surveys to "feel" our market. We learned that part of doing it is sampling and actually reaching the sample or target group. And we had to do it manually. I remember, we had to go to some villages and knock on doors, hoping to get a ten-minute audience in every household. These days, it is a lot easier to peruse Mailing Lists that are available with companies such as martinworldwide. But this is of course for the bigger companies who have budget for Research. For a fee, the company can provide those who need it with a compilation of consumers that will eventually lead to higher sales (because the client gets to target the correct group at first try). This is efficiency and leads to lesser costs, don't you think?