Call me crazy, but it actually made me giddy the one time someone on dA commented 'FIRST!' on one of my paintings (they also made actual commentary, but that's kind of beside the point for the purpose of this thread). I guess I just see cries of 'FIRST!' there as a sign that the piece or artist in question is good enough to warrant someone thinking they have to rush to comment first before others flood in or somesuch. My stuff rarely gets comments, but that person apparently assumed it was going to, and I take that as a compliment.
In other places? I think the whole 'first' thing is just harmless fun. I don't see it as real spam or trolling or anything. It's just something some people like to do, and it's not hurting anybody like real trolling might. :/