This is not to subtract from your probably very correct assumptions but just to add that there may be other reasons.
I recently had a post moved and it was due to neither. I rarely frequent the sales threads and I totally forgot that there as a RAOK/WTB section.
I'd also like to add that it appears as if the "For Sale" thread has more activity than the RAOK/WTB thread and persons noticing this may risk posting incorrectly in the hopes of being seen by more possible "request fillers".
gt_turbo: You're right about that. I'd consider all of those other incidents to fall into the 1% category instead of the 99% laziness.
When I said laziness, it's not an insult on all. But I really mean it. Moving dozens of posts a day, the moderation team is able to pick up on patterns and figure out what's going on. It's always clear when something other than laziness is involved.
Kubla: Click the exclamation point in a little red triangle. No one else will be able to see that you've reported something. It's supremely useful for alerting the moderation team to problems.
As far as RAOKs go, do what I've always done: Give things away to the person who responds & fully handles a transaction (I just mean shipping costs - unless I'm covering that) first. It's not as fun but it's still a good thing. Sometimes I've had people submit photos just to prove they aren't going to flip items for a profit but that's about it.