I had to quickly head over to the gambling section to check how many threads will fall under this category.

For the Main Gambling board;
I found just one thread in the first page which goes beyond 1000 pages.

On the Gambling discussion child board;
I identified 6 of such threads in the first and second page on the board.

The way I see it, not counting signatures in this threads anymore would just push spammers to post on other threads and the cycle continues till those ones gets above 1k pages. Rinse and repeat again.