Why would you voluntarily give the AI bonuses like that with no benefit to yourself?

So basically, if you research it first you have to give it to everyone to get the benefit. Same as Alliances - it needs both sides to have access to the tech before it can go anywhere...

I trade those techs even to those I never wish to form an alliance.  I really dont think the AI is smart enough right now, to band together in an alliance to try to stop you.  I prefer to trade away things like trade and diplo techs, and NEVER give them research, pop, approval, or manufacturing techs.  I always research all defenses, so I will trade away the defenses that dont counter "my frickin lasers".

I tend to hand over large tranches of techs to the AI at various points, just to try and make them remotely competitive.

Oh, I don't do it for a relations boost, I do it just so they're able to build up. I regularly outpace the AI's tech level in the opening 50 turns or so, and then give it a ton of techs just so the game isn't completely one-sided.

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It is happening in my current game right now.  Iridium gave economic treaty tech to me as a gift.  One turn later, I open up the diplomacy screen to make a deal, and find that I am able to offer them a free trade agreement, but I cannot choose to have them reciprocate-- it's not in their list of items.  I think it's bugged pretty good. 

When I offer them a free trade agreement, I also can't tell if I am actually losing 5% of my research and wealth and giving it to them, or if they just gain 5% from the "free markets" without me losing any.