I am not sure this is really a bug, but there are, for lack of a better word, serious loopholes in the AI's ability to employ rational self interest. Apart from the obvious bite the hand that feeds you behaviour two huge things stand out.
1. If you have a declaration of friendship with a Civ you can trade income for gold on a 1:1 basis. So, say you are playing a marathon game where deals last 90 turns, you can offer a friendly Civ 1 GPT for 90 gold UP FRONT! There is no advantage to the Civ in buying your income and yet they will offer you the exact amount of gold most times that the deal is worth (if it lasts the full 90 turns). I have bankrupted Civs of thousands this way. Not only that, once you establish this deal they keep coming back to renew it.
2. Competing Civs do not seem to understand competition in culture and the benefit of Open Borders. Again, with a friendly Civ you can offer them a few GPT in exchange for their borders being open while you keep yours closed. Eventually, as you renew it, they let you drop the price. You quickly achieve a situation wherein all friendly Civs in the world grant you open borders each for 1 GPT, while your own borders remain closed to all. Obviously the 25% bonus to your tourism effectiveness alone should be worth more than this pittance, but such is not incorporated into their system of evaluation.
These are things that are not precisely bugs, but are serious issues with game play that invalidate the AIs competitiveness.
1. If you have a declaration of friendship with a Civ you can trade income for gold on a 1:1 basis. So, say you are playing a marathon game where deals last 90 turns, you can offer a friendly Civ 1 GPT for 90 gold UP FRONT! There is no advantage to the Civ in buying your income and yet they will offer you the exact amount of gold most times that the deal is worth (if it lasts the full 90 turns). I have bankrupted Civs of thousands this way. Not only that, once you establish this deal they keep coming back to renew it.
2. Competing Civs do not seem to understand competition in culture and the benefit of Open Borders. Again, with a friendly Civ you can offer them a few GPT in exchange for their borders being open while you keep yours closed. Eventually, as you renew it, they let you drop the price. You quickly achieve a situation wherein all friendly Civs in the world grant you open borders each for 1 GPT, while your own borders remain closed to all. Obviously the 25% bonus to your tourism effectiveness alone should be worth more than this pittance, but such is not incorporated into their system of evaluation.
These are things that are not precisely bugs, but are serious issues with game play that invalidate the AIs competitiveness.