The items Apple will start off with, are accessories which are low volume, lower priced. If theft in this scenario would be a problem tomorrow, then it should have been a problem today; as Apple only gives you an email receipt and I have not come across a scenario where I had to show the receipt on my way out. Hope that answers your question.
This move is only disruptive if it replaces a good chunk of current usage... without handling common and higher margin items, this is not going to disrupt anyone, just streamline Apple Store processes.
