Let me go down the list of some kinds of startup companies from Start-Up 100 and why they're stupid.
Advertising and Marketing
Right off the bat, a bunch of useless bullshit. I don't ever WANT to see an advertisement or marketing. I want to be able to find that shit if i'm looking for it, but I don't want any of it to just show up somewhere.
Audio and Media
More stupid "web 2.0" websites based around music and other crap. Internet radio has existed for well over a decade. I don't need another place to not find the music I want to hear. (Pandora sucks, Spotify sucks, Grooveshark sucks... it all sucks. I'll turn on Shoutcast or Last.FM Radio if I want random music that I kind of like)
Education, Recruitment and Jobs
First of all, if you didn't get a normal education, some web 2.0 shell of a company probably isn't going to educate you any better. We have Dice and Monster, and people who are competent at what they do will network and find jobs in person like normal.
Enterprise: Security, Storage, Collaboration, Databases
Finally, startups intended for technology. Too bad all of them suck. Most people i've seen who try to develop startups have not worked very long in tech so they design or implement poorly and if they survive it's from sheer luck. Most of these solutions are crap or unnecessary.
Finance, Payments and Ecommerce
Again, i'm pretty sure all the big contenders have already been created. It'd be interesting if they actually had a new way to deal with finance or ecommerce, but most of it's been done and there's not a lot of room for innovation.
Gaming, Virtual Worlds
Ok, here's something that actually has promise. Make a stupid game which is addicting and make a billion dollars like Rovio.
Social Networking and Collaboration
JUST. LET. IT. DIE.
Social networking is a fad. You know what the original social network was? AOL. Just let the shit die. God I hate social networks.
Travel and Transport
I guess there's still a few niche/boutique businesses you could start in this space. But if it's another "how to look up cheap flights" website, just kill yourself.
What I would like to see more of are startups that are intended on bettering mankind, or fixing a common problem, or pioneering a new technology (a *real* new technology, not just a new shitty website or NoSQL garbage tool nobody wants). Medical device startups are really cool. Startups that develop technology for the 3rd world are cool. I'm still waiting on somebody to build a company that just services new companies, giving them turn-key solutions to build new networks and support them. I'll go work for them.