Just bragging rights, I guess. 

It'll most likely be Theymos, depending on how much he posts.  He gets showered with merits whenever he does post, but even still it would take quite a while to reach 10k.  I'm about 25% there, but I got 1000 of those merits airdropped to me when Theymos rolled out the merit system last year (I'm stating this for those newbies who might not realize it).  Earning merits isn't easy, nor is it consistent.  I get them in spurts, often going a while without receiving any at all.  I might reach 10k, but it would take years to do it.