I abort about 25% of my potential posts. In most cases it will just be some smartass comment that contributes little to the thread.
I’ve killed more than a few posts, mostly in Great Debates or the Pit. Sometimes it’s just not worth it to write a post when whoever you’re addressing it to is already convinced that they’re right and anyone who disagrees with them is a racist homophobic communist hatemonger who has ugly toes and doesn’t love their momma and probably doesn’t even know Jesus, either.
Not nearly often enough. I often submit ill thought out or simply lame posts just because I’ve written them. Then I sweat out whether or not they made me look like an idiot. ('Bout 50/50.)
I mostly don’t pull punches that I’ve already thrown, especially MPSIMS and IMHO. I fear posting in the Pit and get bored with GD.
So about 10%
Should I submit this? Am I posting just to post? ARRRRRG
I do it a lot. Especially in the pit.
But I usually take a second to read anything that is emotionally charged (for me, anyhoo) and sometimes I think “I don’t want to go there”.
I type up lots of replies in GD - but then decide I don’t have the time to spend defending them and arguing the inevitable points that will stem from my post, so tend to leave it for a while then not post it at all. Usually by then someone else has covered the reply I was going to give and I can let them continue the discussion with me merely as an observer rather than a participant… It’s a bit of a cop-out really, but I feel if I am not willing or able to hang around to defend my posts I really shouldn’t just throw them into an existing thread as a drive-by. Probably ends up I post 3 for every 5 posts I type up. Quite a lot goes unseen.
Of course, I have little qualms about posting nonsense in other forums. 
I only rarely do a Total Post Abort. Much, much more common is for me to get about two or three sentences in, pause, think “nah,” and stop–I’d say that’s easily half the time I ever click on “post reply”.
Maybe 1 in 20.
Mostly I’m in the Pit and I get angry and then I type it out. After I type it I try to proof it because I know when I’m angry my typos generate like those rabbits on the Visa commercial. Then I get pissed that I can’t spell worth a damn and erase the entire post.
Since I am new to the SDMB I have only posted once (this will be the second!). I have typed and deleted about a dozen, for many of the same reasons as you all have posted above. I’m used to a Cruise message board that I have been addicted to for about 6 months now where I know most of the posters and have a regular chat group/thread. I will say it was QUITE a shock to see some of the titles of your threads and even more so the content! :eek: It’s soooooooooo different here…and by different, I mean good, in a bad way - lol! I mean, you can’t curse on a lot of message boards and I say what FUCK is THAT about!?! I need to say bad words sometimes. Spank me. 
Thank you for your time. I’ll be lurking…
Have you considered the irony in this question? How many more answers are we not getting to read because the almost-poster cancelled them instead?
Are those non-answers part of the answer space? They seem particularly relevant to this question. They’re a bit like the unheard tree falling in the forest.
About four a week. Usually it’s
a)a joke that pulled up lame,
b) a post that contributed nothing new, or
c) something I’m not at all sure of, and couldn’t document if I tried all day.
Once or twice a week, I post something I wish I could take back. Such as in the “What killed hats” thread. Boy, that was really dimwad. Eeesh.
That’s about right. Of course, “some smartass comment that contributes little to the thread” describes the other 75% of my posts pretty well…
At least 1 in 4. Usually for all the same reasons as others have already said.
Including not adding anything that hasn’t already been said. 
And the posts that are unfunny smart-arse quips, or the ones that come perilously close to revealing I don’t know a thing about what I’m talking about, or the ones that are just getting myself into an argument that simply isn’t worth the effort.
But isn’t it good to know that there are Dopers out there who do do a garbage check on their posts before clicking on submit? If only we could get everyone else to.
In GQ, rarely. Everywhere else, I’ve probably written about 4 or 5 times as many posts as I’ve actually submitted. In some cases, it’s a simple matter of having typed out something lengthy, and upon trying to submit it, find that the hamsters were having a stroke or something, and my post is lost. At that point, I usually don’t bother trying to resubmit it. Other times, I preview and preview and preview, then simply decide no one cares, and delete it.
Once a week or so. Almost invariably it’s
because I thought of something funny but no matter how much I tinkered with the text I either couldn’t quite get the joke across the way it was in my head (I’m pretty anal about making sure my jokes are phrased just so; timing is everything in humor, and timing is controlled in reading by rhythm of phrasing), or because the joke is somewhat dark or off-color and I couldn’t figure out a way to express the humor while simultaneously making sure it wasn’t intended to be taken seriously. Sometimes in the latter case I’ll indulge in a smiley, but most of the time I just jump out of the cabin and ride the zip line to the ground.