"Criminals across the UK have hacked the new keycard system used to top up pre-payment energy meters and are going door-to-door, dressed as power company workers, selling illegal credit at knock-down prices"

“It grows every day. For us, you could add 500 more each week. If you multiply that nationally to other main companies, it’s a massive problem.”

http://www.schneier.com/blog/archives/2010/09/new_prepaid_ele.html (including informed comments)