I am not a my little pony fan, but I think it would be a great idea.
You guys are seriously undermining the "Brony" fanbase if you think its just for 5 year old girls. Honestly, one of the my little pony creators was surprised at the fanbase as well, but was happy that everyone is enjoying the show.
I think they actually had something called Brony-con or something to that effect, I forget (wikipedia, how I should use you now).
My little pony has male and female adult fans, and quite a fan base. Every time someone asks why, the reasoning is that it is a "well written show" and/or they "enjoy the plot/story."
Could get a little weird with my little pony items making their way around PSH, but hey to each their own.
My thought on the whole thing? You are never too old to be entertained by anything if you really like it. Growing old is inevitable, growing up is optional. For whoever likes it, great. If its a hobby and you can afford it, more power to you. If it comes to Home and brings in new users because of it, then that is an added plus... So go nuts!!!
My one "thought" in response to this topic. - http://www.youtube.com/watch?v=XfRl6y3peRc
I think they should add some clothing for brony's to represent themselves. Hopefully not just T-Shirts
Being in my late 30's, I don't know if this is a really good idea. I'm not saying that someone couldn't do this, but I don't see alot of these going like hotcakes!