Tim Bray's ongoing is providing tons of inspiration to me. I just found a brilliant observation on software writing : Writing the Hard Line of Code. Amen to that. This is exactly what happens 9 out of 10 times. Of course the reason one does this kind of thing is that last 1 of of 10 cases, where the flow gets you and that is sufficient for wonderful things to happen.
If - like me - you have an excessively verbal inner life, the same kind of thing happens in 'plain old writing'.
You're arrested by something and get the feeling there's a decent point to be made, and you sort of know what it is, but it is tied in with too much internalized knowledge to get onto paper in the next hour or so - my usual limit for stretches of continuous good prose.
So you start to express some of these internal prerequisites hoping the flow will get you to that point you were looking to make. And you then often find that the point either does not carry as well as you hoped, or you just don't get to it - caught up in all the marshalling.
The 'verbal inner life' thing comes into play because, in this mode of thinking you're always adding story threads to a dense forest of other threads. Nothing is just an observation.
Thank god we have blogging and hypertext to deliver us from this mess of setting up your stories...