I've had the spy ring event (the one where an agent appears on almost all of your planets) happen in 3/4 of my games, which seems a bit frequent. Also, in Huge maps and larger this can lead to a very very long list of spies. I have had as many as 62 spies that needed to be gotten rid of. When the maximum number of spies you can produce is 1 per turn, if you can afford that kind of cash, it takes forever to get rid of them all.
Also, I noticed that some of the AIs are willing to trade away a bit too much of their influence. I don't know how much this had to do with me being chummy with the Terrans, but as the Altarians I was able to trade for 3/4 of their influence buy selling them world colonization techs in one turn. Some of our worlds were intermixed and this lead to the defection of Earth and, eventually, about 80% of their planets to my side
I also wonder if these advanced colonization techs can be weighted based on the number of planets in the map that use them?