Well, by random I did not really mean to say that the proces behind it is random, just the result to any observer. Popov explained it pretty good in this threat:
So what I meant to say is that somehow this process of “random” firing of the neurons in REM seems to trigger and influence our dreams, but that the inlfuence can be cut to some extend by becomming lucid. I agree though that there also has to be some process that has to organise all the signals during REM into somewhat coherent stories. On a side note, did you ever notice that this coherene of dreams is far less in the early REM dreams then in the last cycles? I find this to be a curious phenomenon.