PIF: Play/Pass It Forward
This is done on a message board.
A person starts the thread with items she has up for grabs.
If the next person on wants an item, they say so BUT they must post an item to send out to the next player who comes along and wants it.
There can be many readers of a thread like this but only the players are random, depending on what
they want, and what they are willing to post and to send out.
Time element: These can go on for a short specified time, or an extended time.
Similar to a DAK Swap