Check your map settings and the number of factions. It also depends on the map, I've had games where everyone was on top of each other, I've had others where I had to explore 50 turns in one direction before bumping into even a minor AI.

There's also some larger than large maps in the mods you can download. 

I've been playing on large maps since they became available and my impression is that even if there are a limited number of 'canned geographies' in the map set, the placement of stuff that's not a geographic feature is fairly well randomized. Just like Archonsod, I've had some 1.0-1.06 maps that seemed empty of other factions and others that were so crowded I ditched them pretty quickly on account of my turtling tendencies.