One person says they can do the last person's task, but only if somebody else does something for them. Then the next person does the same. (Says they can do the last task, but only on a different condition.)
An example of how this is played:
Poster 1: "I could give you a massage, if somebody would give me Half-Life 3."
Poster 2: "I could give you Half-Life 3, if somebody would make it."
Poster 3: "I could make Half-Life 3, if somebody would help me concentrate."
I would start this game, if somebody could post something awesome…