I use my debit card to guarantee the room because it is the number that changes most often. My bank, or the stores I shop at, consistently get attacked or hacked, so it is easier to just leave that floating on the web than individual credit cards.
OK, but I'm not going to give anyone access to my banking account which is what using your debit card does in this case. I'd rather deal with a hacked credit card than a hacked debit card and have checks or automatic drafts bouncing....