Poke marathon occurs when two ppl keep poking each other back on facebook, may go on for a zillion years...
"you've been poked by a"
b -ohh i have to poke back!!
.... .... ...
"you've been poked by b"
a -oh i have to poke back! poking is fun!
.....
"you've been poked by a"
b - =___= another poke marathon!