You'd need four bytes of height data for every point in order to produce nice rolling hills. You'd need at least another couple of bytes for surface information like texture mapping / foliage / surface behavior etc. This will hold data defining the surface, letting the game know that this little patch of land is made up of grass, mud, clay, or one of a dozen different colors of rock and dirt. Then there will be a few bytes for controlling the placement of shrubs and trees. This is a really conservative estimate, and in practice you can easily end up with a lot more than that. But assuming just twelve measly bytes per point - each single one meter square of the terrain taking less data than the sentence you're reading right now - the final size of the gameworld comes to 196,608,000,000 bytes of data, or about 196 gigabytes. You would need a stack of around forty DVD disks just to hold the terrain.
And then you need the roads, which will consume at least a couple more gigabytes. Plus the buildings, road signs, vehicles, bridges, and other infrastructure. Plus the game itself. We're looking at a stack of 45 DVDs for a game this size. Perhaps the "Gold" edition of the game would ship in its own collectible wheelbarrow.
Obviously, this game wouldn't even be possible without procedural content. Forget about building that much content by hand, which would take an army of artists. Indexing and accessing that much data and serving it up on demand at the speeds required by a racing game wouldn't be a picnic either.
Procedural content takes time to make. No, actually the technology takes time to make. Once you have a world-generating tool, content is free. Feed it some scraps of data and tell it how much world you want. The idea here is that it won't magically make games cheaper to produce, but there is hope that it can give us a lot more gameworld for the same money.
On one end of the spectrum is the Valve Software approach to games. Everything is meticulously hand-crafted and polished to a mirror shine. It makes for some nice gaming, but it takes forever, costs a fortune, and doesn't offer a lot of gameplay. When Episode 3 finally comes out, we'll have waited three or four years for what? Six hours of gameplay? Maybe ten. I'll be glad to have it, but it would be nice if we could get more game in less time. On the opposite end of the spectrum is Spore, which offers limitless variety but it all sort of feels the same. (Disclosure: I haven't played Spore for various reasons. I'm going by the reviews I've read here and elsewhere.)
So up until now the choice has been: A) Lots of bland content for nearly free, or B) A bit of dynamite content for excruciating development costs. The FUEL formula suggests a nice compromise between the two, with a bit of hand-crafted work to give the game character, and the rest filled in with broad strokes from a procedural engine of some sort. Applying this to a shooter, you might have key locations in the game (boss fights and plot points) take place in carefully crafted areas, but turn over the generic tunnels, boiler rooms, sewer levels, and outdoor areas to procedural code. Those are places that players usually breeze through without a second glance, and it doesn't make sense to pay a room full of level designers to labor over those if their talents could be spent on the areas we actually care about. The handmade stuff is the steak, and the procedural stuff is the free bread the waiter will bring you to make sure everyone leaves feeling full.
I'm really excited to see time being spent on technology other than graphics. Graphics have looked fantastic for the last few years, and constant increases in hardware and development costs hasn't seemed worth it in the face of such modest visual nudges. Yet we've hardly scratched the surface of what could be done with procedural tech.
Shamus Young is the guy behind this movie, this website, these two webcomics, and this program. His dream is to see the FUEL tech used in something like Fallout, so he can have the full 118km2 post apocalyptic "Mad Max" experience.