I only read the first page and a bit of this, so forgive me if I repeat some things.
I've been to Expo 5 times varying, first time I stayed indoors a lot, from my memory, there were no free hugs, and not many cosplayers (But the ones there were pretty good )
I was very intrigued by the Expo, and I was about 10/11 that time (Go young otaku-kid!).
So, next expo, I cosplayed and I was really into it. I was wary of perverts of course, and I did have a free hugs sign, but I don't think any free huggers caused any problems, because they basically had a sign with the meaning "You can hug me" but of course, they can be turned down. I found that a lot of fun, and made one or two friends.
But in October this year, I found myself incredibly uncomfortable with newer expo-goers.
One of them I kept bumping into, kept reenacting obscene stuff with her boyfriend (At least, I assume it's her boyfriend) i.e. Moaning loudly, grinding against each other, you get the idea.
I had to fight off the urge to yell at her, because 1) She looked very young, must've been 11/12 2) It was a big nuisance to me. 3) What the hell, public indecency much?

Even in my age range 12-20, I'm still yelling at girls my age like an old-timer, shaking my fist and telling them to "SHUT UP YOU DARN WHIPPERSNAPPERS!"

TL; DR: Maybe it's just me, getting too old, too quickly, but I think there's something amiss with the new generation xD

Hey, I'm nearly out of 'that' age range, and I don't actually think it has that much to do with age. So, since its sorta late and I have time, here's my mental 'groups' at Expos (excluding other events since this seems to mainly deal with Expo)

1. The people who are actually true fans. This includes cosplayers of any age who spend time and effort on their costumes, but also the people who may not cosplay. I mean, there's other stuff to do than cosplay at Expo...

2. Newbies/Families. By this I don't mean to insult newcomers(hence the non-n00b spelling ID) People who are first-timers, who may bring their friends or families and are a little nervous about everything. The first impressions are usually lasting ones, although I do feel a little sorry for people who have to bring company that is not interested in any aspect of the expo. Its nice to be with friends and do/attend something you love. (I'm a sap.)

3. People who come to Expo to socialise. Call them free huggers, obnoxious brats or leeches, it doesn't really matter, they all end up doing the same thing anyway. They are the people who aren't necessarily interested in anime or manga, and if they are, its the ones that have been mainstreamed (I always feel like Bleach/Naruto have been raped, I was a fan back in the day!)
But in general, these people are a younger generation, yes, but not everyone 12-20 acts like this. Its incredibly attention-seeking, irritating to others, but its their own delusion of freedom. I'm pretty sure most of them will grow out of it and lose interest in anime/manga all-together, or quietly become a member of 1.

Anyway, I hope that made sense, and yes, its pretty much this whole thread chewed over, but I thought I'd add my salt. There. Tasty.
And yes, I'm heading to bed before attempting more crack theory.
~aya~