I went to Walmart today to get the new Power of the Daleks dvd. It was already gone. I asked an employee and she looked in the back. I waited about 30 minutes before she came out and said that there were no more. It just came out today and they sold out here. So either:

they only had 1 or 2 copies in the first place (which would be especially sad since they had 100 copies of Boo! A Madea Halloween right next to where Power of the Daleks was before it sold out)
I underestimated the number of Whovians in my small town.