I wanted to see how many members had boardmarked the XKEM board. I found the "TOP BOARDS" list and saw a SCORE number of 1501.
Not sure that was for boardmarks, I did a test.
I removed my boardmark forXKEM and checked the TOP BOARD SCORE number again. Sure enough it was lower, but to my surprise it was lower by two (1499), not just one (1500).
I then added XKEM back to my favorites and viola, the count had gone back up to 1501, again being incremented by two instead of one.
It also looked like it allowed me to as the same board to favorites more than once. I would think you would gray-out the link to add a board to favorites for members that already had added it to their favorites.