Baalz is right, being a vet gives you a red flag. There will surely be other ones that will do diplomatic attempts to try and organise smth againt a vet

Well, unless you are llamabeast
Also behaviour in old games means a lot. If you tend to go AI when things start to go bad, you may be sure that you will get attacked only for that reason in one of the next games. It's really basic psychology. And invader will prepare nice big show of fireworks, to try and convince you to go AI and let him win fast. Same goes the other way round - someone who fights till the end has smaller chances of being attacked, unless he is really outnumbered.
Executor:
I have a practice in that now. I somehow got into me vs. everyone else situation. Some people went AI, including those that had to be my vassals and blockers from other players. I wasn't really prepared for that and it will be tough job. Map really doesn't promote small controlled fronts [and there were some bugs that complicated my situation].