Well, I think Andrew started it. At the top right hand corner of your post is the post number. When it hits a number ending in 500 or 000 number its a pirate for whoever posted. You will notice a swarm of killer bees come out just as we get to within 20 posts of this. Although, of late, the board seems deserted and just as you reach the magical post, people come out of the woodwork with impeccable timing and snags the pirate away (sneaky pirates). Argggg......

Helenititis is when you start posting like 10 times in a row trying for that pirate. Helen is MrsJobba who is gone on vacation right now and so can't defend herself.
On page 1, post 10, Andrew lists the pirates won to date. Post 5000 is coming up, and its a biggie.
ETA: Oops, got that wrong, When the posts end in 00 or 000 is a pirate.