Well, opinions vary. Maybe it's just that I'm 35 and was a kid in that era but I actually like 80s fashion, for me it's always been Disco-type fashion that bugged me.
I don't think there is anything in paticular that bothers me that I can think of apperance wise. The issue is usually a matter of a person being able to pull off a look or not as opposed to the clothing itself. My problem with trends is when you get the copycats who just look stupid doing something, even if it works for some people.
Things like Crocs don't especially bother me, the whole point of those is to put comfort over apperance, and I can actually respect that. If people are wearing them because they are comfortable for them, that's fine, if they are wearing them for some style related reason then I think we're looking at stupidity.
Sometimes fashion statements bug me even if they look decent, due to the meaning involved. I tend to not be a fan of "dressing for your politics" so to speak. Someone who dresses in multi-colored "traditional african" garb to make an empowerment statement is an idiot when they can't pull off the look (which a lot of people can) as an example. For some people it looks decent and is fine though, the problem isn't the clothes themselves.
As far as things like the "broken 3D glasses" that's a grunge thing, I think it started with Nirvana on one of their album covers or posters. It's not supposed to make someone look smart, so much as be hip by wearing something that should rightfully be considered garbage. The statement of wearing regular 3d glasses, especially the old paper ones, is something almost nobody can pull off, but it's an artsy thing about seeing the world differantly from everyone else.
The Fedora thing started with Columbine and the "Black Trenchcoat Mafia" it's right up there with the black dusters, and/or little tommy gun pins. A lot of people can't pull these various fashion statements off and it looks stupid. The intent (like the african thing above) was originally to protest the treatment of those who were differant, and show some subtle support for the killers, or at least why they did it as opposed to what they did. That's a whole loaded political can of worms, and truthfully I think a lot of people who do it don't even "get" why the trend started to become part of nerd chic to begin with. It's kind of funny to see some nerd wearing a fedora, who loudly, passionatly, and vocally speaks out against Columbine if asked, which has happened. If you want to make that statement I actually encourage people to go with the Tommy Gun pin (which are becoming a little harder to get) since it's not dependant on your abillity to make the look work. Few things are more pathetic than fat kids in capes (or black dusters). I'm also far less judgemental of this paticular statement than I probably should be, simply because while I don't care for the killings, I think society missed the point entirely and has been bringing this kind of thing on themselves. We really need to see some changes to the school system, and enforcement of school policies, even if it leads to uncomfortable issues like schools losing money/donations due to say expelling entire athletic teams.