So my question is would any of you seriously suggest to the novice GM that he do no world building before running his first game?
For a novice DM, I would suggest getting a good starting adventure (like
Keep on the Borderlands or
Sunless Citadel), reading it thoroughly a couple of times, imagining what the players might do in certain situations and sort of playing through the module in their head and possibly adding side adventures or interesting quirks to the adventure to make it their own.
I would suggest having a good working knowledge of the immediate area around the adventure site (like the Keep or Oakhurst) so the budding DM has a solid foundation from which to improvise if necessary.
I would suggest coming up with a few adventure hooks to sprinkle into the first session that may lead to the PCs next set of adventures.
I would not suggest "worldbuilding" in the sense that the DM needs to know what the legal system looks like for the kingdom on the other side of the continent from the adventure site. I would not suggest the DM spend significant time developing details about any items outside the immediate area of the current campaign.
I would also not suggest the worldbuilding + sandbox method where the DM provides no guidance to the PCs at all and tries to come up with a world description detailed enough that he can use it to run any adventure, anywhere, whenever the PCs wander into that particular area of the world.
Finally, I would not suggest that the DM do no thinking about the world and try to run a gaming session using 100% improvisation to create an adventure on the fly for the players, with no background information to use as a foundation whatsoever.
:edit to add:
One of the things that I find confusing is that people are drawing a dichotomy between worlbuilding = prepared and no world building = improvisation. I find the relationship between those two things to be exactly opposite. If I'm doing a lot of worldbuilding, it's usually because I'm expecting to do a lot of improv at the table and I feel I need a larger base to build that spontaneity on. If I'm, instead, preparing specifically for an adventure locale and ignoring the larger world, I usually end up having to do a lot less improvising.