There is a lot of work which must be done up-front to make it successful and, as Mike has pointed out, risks still remain. Every time you take a slice the potential for non-representativeness increases. Plus if you are not going to be using it often or have a lot at stake, the costs may be prohibitive. As I said, I have had a lot of interest in this method of late, but most people end up walking away with a severe case of sticker shock. Those who have used, however, seem to be coming back for more.
All samples are biased, just in different ways.
There are people who won't answer questions on the phone, but will answer them through the mail or in a questionnaire on the Internet. So it's pick your poison. That doesn't relieve us of the obligation to do the best we can to pull as representative a sample as we can, but sometimes the cost and effort seem not to be worth any improvement in accuracy. So far, panelist response has stayed right up there, though we have seen some fall-off after the initial rounds, where we were getting all but one or two. In the latter, some of the researchers are finding it necessary to send out follow-up reminders.