1) research pact gives you a free tech when complete. Also bugged right now, so gives tech on DoW. But I'm sure they will fix.
2) Because tech trading/brokering was horribly unbalanced and exploitive in previous civs, especially 4.
3) You can see what civs have excess resources quite easily in the diplomacy overview.
4) Because you are a rival,, and therefore a threat. Quite realistic actually. Can you think of any examples in history of close neighboring civilizations that aren't rivals?
1) Hadn't even noticed the bug... But was referring to the "secrecy" and "cooperation" pacts, their nontransparent effects and the fact that you have no idea of the other civs' attitude towards you before they DoW on you.
2) Care to give any basis for that reply?
3) No you can't, you'll have to enter negotiations before seeing that. And if you can, please direct me to the correct screen. And when I have to ask this question in a discussion forum pretty much proves that at least the diplo UI needs work.
4) With the possible exception of Sweden and Finland, largely true, but at least those countries know why they hate each other. Civ 5 doesn't tell you. Besides, I was giving an example with the Chinese and Aztecs. I currently have no way of knowing whether they love or hate each other (or me, to that matter). Or do you mean that any civilization takes offense if I trade with any other one = their rival?