For me it seems like several tend to die (or give up) easily somewhere early on in the game. (not too early, but when compared to the full game) It also tends to happen to the factions that I have a chance at allying with as well. :/
Does it also seem that the Normal difficulty tends to be harder than usual? Sometimes I do ok, but other times they just somehow quickly own half the map and crush me easily....WTF?
(not to mention some AIs still like to gang up on me, one attacks a planet, so I deal with them while another decides to attack my other planet on the other side of the map. Once I finish off one player, I go after the other attacker, and the other guys come back with a full fleet again.... :/ )