I can honestly say I had no issues whatsoever with this system. It provided a very positive experience and service. I had no issues giving my credit card for this purpose -- it's not used for anything else but to guarantee your room. Besides, in this day and age, if you don't check your Online Banking for your Debit/Credit cards on a regular basis (and I don't mean once a month), then that's your own problem.

If you're uncomfortable with doing this promotion, then just don't participate and pay the regular rack rates or various public offers. Simple as that.