We've got all these pretty colored borders on the starmap, but they mean next to nothing. I can cross them with my war ships. I can engage purple's shipping in red's space. I can pre-position whole fleets on yellow's planets befor declaring war by attacking him. Etc....
Aside from the occational UP resolutioning that taxes starbases in other's territory, and of course, the influence victory, I really don't see any other point to the borders. It seems that the game engine doesn't register the fact that 20 large warships parked two cells aways from an alien planet doesn't represent a threat.
Here's a scenario where I think borders would be emplyed:
You've got a recalitrant neighbor who just doesn't want to be nice, or doesn't want to share his techs. So you park a fleet on you're shared border, and ask again nicely. The AI should be able to recogonize that he either complies, or he's about to get bashed. As it is now, my entire fleet could be engaged on the opposite side of the map with another race, and still be considered the same threat to the race sited in the scenario.
Also, If I cross Red's territory with war ships to get at green, Red should get REALLY pissed. And if I actually engage greens ships in reds territory, red should get REALLY REALLY pissed, and should probobly consider it an act of war against him. Perhaps another form of treaty could be "safe passage"
Another benifit of borders might be more prolific appearance of anomalies after the game has started. As it is, my flag ship is pretty much parked once the game get a few weeks old. Also, snatching an anomaly from anothers space should incure a diplomatic penalty of some sort. I've seen that come up for discussion in the UP, but otherwise, any anomaly is fair game.
Please make borders mean something more!
