The way this was demonstrated there was no data-flow control on the N900 side of the transaction. So if it works like this in general then it means that anyone who gets close enough could just dump whatever they want into your N900. Not nice.

So the technology would need something like what's used for BlueTooth, i.e. either pairing in advance (unlikely for the kind of buy-from-store service demonstrated in the video), or a pop-up & accept on the receiver (N900) level. In other words, never as simple as demonstrated in the video.