Yea, I think comments aren't allowed after an amount of time (which may be changed with an future hard fork.) To answer your question:

Why is there so many members wanting to be witnesses when there is a top 15 .

Technically it's the top 19. Witness are paid for each block they produce. Every 'round' which is over 63 seconds, there are 21 blocks that are created. From these 21 blocks, each of the top 19 witnesses are guaranteed be assigned to create 1. One is assigned to a miner in the mining queue (so this gets spread around between those that sign up for this...I believe.) The remaining block gets assigned to a backup witness that is outside of the top 19, so they don't get one every round. However the more witness votes (proportionally) determines how often that backup witness will be selected for that extra block. Hence the person at witness rank 20 will get the block more often than a person ranked 35 (of course assuming the don't have the same weighted witness votes, which I've never seen happen and doubt will happen.)

Yep, feel free to use the link. Hope it's helpful...I'd just recommend a disclaimer that the specific numbers are off (i.e. how much witnesses make) since pre-dating the economic changes. I did edit it the post at the time with the comments that were given to make it as correct as possible for the time.