That’s the same with me. I figure, either it’s a debate or a really hard question that I probably can’t answer. I mean, all these people ahead of me tried and it’s still going…
Otherwise, my opinion will probably get skimmed over and not even noticed. And in that case, why bother? 
Anything anime, comic book, 20-something hipster tv shows or sci-fi.
No interest, don’t get the references, don’t care.
I almost didn’t open this one, ironically enough.
GuanoLad and descamisado, stay strong, guys. The OOTS saga is quite a chunk of graphic novel to swallow; and the chances are that it would more likely swallow you. I’ll concede quite readily that getting up to speed on it was a huge time-suck. It was worth it for me, but I wouldn’t presume to assert that you would have the same response.
Plus, even if you did read all the on-line content, there are still dead tree versions that expand the story quite a bit; you’d have to get your hands on those. AND read the thread on top of it all.
Yeah, you’re probably better off just giving it a miss.
Whatcha Readin’?
Anything about TV shows I don’t watch, movies I haven’t seen, books I haven’t read: LotR, Lost, Buffy, Dr. Who, Arrested Development (let it go!), Harry Potter.
Travel advice, like What’s to do in Kalamazoo?. I hope you have a good time, but I’m just not going to read it unless I’ve been there or intend to go there. I actually never go anywhere.
Threads that question the legality of something petty, like I taped a song off the radio, am I going to prison?, or I found a magazine on the bus, am I legally allowed to read it?
Anything to do with libertarianism.
Off the top of my head…
Anything longer than 2-3 pages
I just don’t have the energy to slog through fifteen pages in order to post something constructive (and I do not want to post without reading the whole thing). In addition, if they haven’t figured it out in 15 pages, it ain’t gonna happen. And it’s usually mud slinging for ten of those pages.
Pure polls such as "What is your shoe size?"
Before the polling feature, these were totally useless (IMO) since I didn’t think anyone wanted to read hundreds of people’s shoe sizes. With the polling feature, the aggregate graph is more interesting than the posts. Kinda cool to see the spread.
IMHO threads that encourage drive-by posts
In line with the simple polls, there is a certain broad category of thread that I can’t easily describe where everyone comes in and mentions their own XYZ, but doesn’t read the other posts. I usually discover these after the fact, posting to them (ooh, neat thread… here’s my post) and then I tire of the update emails that linger on for weeks and I unsubscribe.
Strong left-leaning threads
I came here because I liked Cecil kinds of questions such as “Why is poop brown” and “What’s the purpose of the pitcher’s mound in baseball?”
I did not come here to discuss same-sex marriage and religion. It seems that this board is the place for those kinds of discussions, so in order to get my personal SD experience I simply ignore these topics.
Threads full of SD inside jokes
It’s not for me.
Not that they are always identifiable by the title, but there’s a certain kind of cliquey feel that some threads have that I avoid.
I never go to the Game Room or GD.