Going to put in my 2 cents here (apologies to TS for the hijack-escalation).
To the cosplayers, especially new ones, having more exposure means they are more "well-known" to photographers who are in the "scene". The chances of photoshoots increased greatly, and once there is a mutual trust, both the cosplayer and photographer can do lots of things. I personally know of one photographer who has made names overseas just by being in the scene for quite long.
Personally speaking, this is a free country. Anyone can do anything as long as laws are obeyed and everybody feels happy in the end.
In my very personal opinion, anyway, cosplay events like this is something like a "business convention," where cosplayers wanting to make big can approach for photographers' access. First-timer photographers come in here to "trade" pictures with cosplayers and build up a relationship (working or otherwise).
Updated: About horror stories, *sigh*. Am I the only one who feels like quitting the cosplay events photography scene altogether?
Anyway enough of my rants:
TS, good attempts. D300s has good ISO, so go high indoors. Decent subject isolation on some pictures, but in events like this, best you can hope for is a decent lens that can blur out the crowd.
As for myself, I find my own pictures... "lacking." What was that WTDuck comic that detailed the highs and lows of a photographer's willpower?