I must say I disagree with Shaman to some extent. Specifically this statement...
The "infinitely creative referee" who can adapt to whatever the players do on-the-fly, who can make up a bill of fare full of exotic dishes and the styles of dress of traders from foreign lands at the drop of a hat and keep it all straight a month later, is a myth, a strawman, exceptional beyond reasonable measure. Most refs in my experience tend to fall back on familiar schticks as well when faced with the unexpected from their players, leading to a pretty homogenous (and, for me, dull) environment pretty quickly.(Emphasis added.)
This year I celebrate my 30th year gaming and if I fell back on familiar schticks at this point, none of my players, who travel the vast distances they do, would play at our table. What I tend to do is establish certain parameters of my own to maintain consistancy and then ad-lib nearly everything after that. I love it when players do the unexpected and thank goodness my group (some members having been with me for over 15 years) can still stun me with their innovative approaches to the situations they face.
Granted I am well aware my group is atypical. We have older players, several women and D&D is not one of our staples. But I'll be damned if my players ever walk into a space port bar and I can't name the bar, come up with colorful patrons and start an adventure based on what they do there in a moments notice. As a matter of fact, I don't really design adventures. I outline ideas I'm interested in exploring and then place the players on a world and see what they want to do. Without some predetermined elements (notes on the planet, it's major cities, it's people, etc.) this wouldn't work, but I don't find it exceptional beyond measure.
Case in point...A group of PCs were in a firefight after being double-crossed by their employers. Concerned they were loosing, the lead PC gathered the group. made a break for the spaceport, got in their ship and left the planet (and the adventure). They hadn't gotten their money, cleared their names or completed other 'adventure goals'. Once far enough away and ready to 'jump to lightspeed', I asked where they wanted to go.
"Where can we go?" they asked.
"Anywhere your ship can reach on the fuel you have." I replied.
Looking at a quick map that had about 6 or 7 planets, one player suggested I couldn't possibly have a set up on all 7 worlds. They seemed to pick one world at random and I said great and went from there. I did not have a set up for each world but I did have an idea of what the ruling power in the region was, the kind of aliens there and the theme or feel of the campaign. Presto! Ideas flood in.
Maybe this is why fantasy never appealed to me. The worldbuilding element is often done in a fashion that is far to rigid for me. Funny that scifi worlds are generalized and worlds of myth and magic are often defined in exacting detail.
AD