This answer suggests popularity growth of people privately exchanging bitcoins for a physical currency, in person. This might occur in "coffee shops, hotels, hostels, hackerspaces, etc".
An example would be 2 travellers meeting in a hostel in, say, the UK. Traveller A has just been to the USA and traveller B is about to go there. Traveller A has US$200 that's no longer needed, so he agrees to exchange it for some of traveller B's bitcoins.
Definitely assume traveller B has a mobile phone or other internet access to perform the transfer, but please consider both cases of traveller A having and not having similar access at the time.
What are the risks of such a deal, and what can be done to improve the chances of a successful deal?