It's actually pretty analogous to actual scratch cards, as mwg66 pointed out here: http://news.ycombinator.com/item?id=2174506 http://news.ycombinator.com/item?

It's actually pretty analogous to actual scratch cards, as mwg66 pointed out here: http://news.ycombinator.com/item?id=2174506 http://news.ycombinator.com/item?id=2174506