[VedalkenBear]

And, well, they sort of _do_ know something you don't. The distribution of sites in a province can be adequately modeled with the binomial distribution, with the following numbers for probabilities in the case of Middle Era default:

0 - 0.1296
1 - 0.3456
2 - 0.3456
3 - 0.1536
4 - 0.0256

The chances that a province will have greater than 2 sites is only 0.1792, and so the computer is programmed to avoid those sites in favor of those provinces that have fewer sites.

It would be nice to see this implementation enhanced to work for specific terrain types, or to simply give the player the choice of threshold.