But Evan created a parameter that allows you to set the transaction lock time you prefer. If you want to lock a transaction for a month you can do that too, this can be great for contracts between people you could send coins to someone but prevent them spending them with a transaction lock that expires at a later date giving you time to check that everything is good with the terms of the deal. You can even adjust it to a 10min lock and use it for POS as you are describing.
Or so many other applications InstantX is really an adjustable time transaction locking system and you can use it any way you want. Obviously the uber fast locking time is how we are marketing it right now but it is much more than that.
Plus, the blockchain still secures every transaction just like we do now. The transaction locking system is an additional more flexible layer, transactions go to blocks normally as they do now. There is no additional risk I really dont get what some users are saying.
http://en.wikipedia.org/wiki/Clearing_(finance)
A blockchain is not a POS system and never will be. http://en.wikipedia.org/wiki/Point_of_sale