What the Good Lord of Alt-Tab giveth us…
Actually, the Good Lord has given us, well, me anyway, a new office. My “alt-tab” key is now called Closing The Door. 
With doors, you shouldn’t have to worry too much about PHBs walking in… right?
This is why I quit doing vanity searches, to avoid the realization that most of my posts seem to have been of the drive-by variety. Portwest hit the nail on the head - I’ve composed more posts in my head than I’ve actually typed. I even sometimes get a few paragraphs down before losing interest and either moving on or deleting everything and posting a short quip that is only funny up to the second after I hit “submit”.
That said, most of my favorite posts are the witty one-liners that passers-through toss into a discussion.
Because, of course, it’s such fun to giggle.
Automatically parse URLs: automatically adds and around internet addresses.
Email Notification: emails sent to you whenever someone replies. Only registered users are eligible.
Disable Smilies: Disable smilies in this post.
Show Signature: include your profile signature. Only registered users may have signatures.
That’s exactly what happens to me MachV, I think I have something witty and important to say, but by the time I’ve written it down and edited the holy hell out of it (the grammar/spelling police around here scare me), the idea is now stale and no longer relevant to the conversation.
I really envy the people who can think on their feet fast enough to get the one liners in where it still makes sense.
I think that ‘hit & run’ is a misnomer, it should be ‘post & run’.
The mathematical definition was mostly just an interesting game and had less to do with the OP’s behavior question. Some drive-by posters are actually valuable contributors to the boards. Others are banned. It all depends on what you have to say and how you say it.
With regards to thread killing, several threads (e.g. this one) discuss “Thread Killer Percentage” and what that means. Again, the statistic is purely for amusement and really says nothing about whether your post was responsible for killing the thread, or if you just happened to be the last person to hit submit.
In short, Big_Norse don’t worry about either statistic. I’m sure every poster has a fair number of thread-killing posts and even one or two OP’s that have no followup at all. If you have something interesting to say, post it. In most forums you won’t get jumped on. I would recommend thinking twice about (and reading four times) any post to GD or the PIT though. Read your post several times and make sure you are tough enough to take the heat.
I’ve always considered a hit-and-run poster to be someone who posts only ONE message at all. I can understand the psychology behind single-thread hit-and-runners - they at least post more than once. But what about the people who have posts counts of literally 1 or 2?
What’s a PHB? I have an office complete with a door. Should I close it to guard against intruding PHBs?
A PHB is a pointy-haired boss, of course. 
Uh oh, someone hasn’t been reading their Dilbert cartoons!
Now where’d I put that angry fist of death???