Having 100+ major factions is an edge case and not what the game is going to be balanced around, I would think.  Still, the obvious solution would be to make the cost of tech be (somewhat) dependent on the number of major factions present.

*cue cries of "Now you're forcing me to trade techs*

The other point is, in the theoretical game with 100 major factions what makes you think each faction will be in contact with each other?  OK, fair does on a smaller map,  But, well, if one is going to cram that many factions on to a map that can't support it, weirdness is to be expected.  But on the Immense and higher maps (which is where I think these mooted scenarios would tend to occur), many factions might live and die before anyone contacts them.  So they probably wouldn't be able to get into a tech trade spiral.

More to the point, as you learn more techs, a "tech tax" is applied making it far harder to research the rest if you get a bunch at the same time.  When I've traded a bunch of techs all at once, it then plays havoc with me trying to research my current ones.  This is a feature not a bug, BTW, according to the devs.

So, yes, it might be that some races will be able to trade their way into, lets say, the Age of War with aggressive trading.  Then they'll slam into a brick wall of not having enough research infrastructure to continue.

And that presumes that all of the races will like each other and not launch into wars of conquest due to not having enough room to properly grow their empires.

...

Mind, I LOVE tech trading, and base quite a bit of my playstyle around it. So I'm a little bit biased here.

You can turn off tech brokering.  I think that is the one that prevents you from trading techs you haven't researched yourself.  I'm not positive about that (lack of tooltip descriptions, hint hint devs), but I believe that is how it works.

I think a lot of this can and will be fixed with fairly simple balancing. If the AI values it's own tech more it will drive the incentive for tech trading and brokering down, and it will only be valuable in very specific cases or when you have a large diplomatic advantage over a close ally.

In a game where I am managing hundreds of constructors, tech trading is no chore.

The AI basically researches the same techs so after a few rounds there is little to trade with them after 40-50 turns. A trade round every 20 or so turns keeps you up to date with them. The AI are easy to manage right now but that will change I am sure.

Along with that, whenever you come to such high levels of micromanagement, it's essentially an unfair advantage against the human player.  The computer can compare techs with all of its neighbors every turn.  Sure humans can do that too, but your game suddenly becomes ridiculously boring.  If the advantage for this comparison is too high, then it becomes annoying to play the game.  Which defeats the purpose of making the game in the first place.

Similarly with making tech trading expensive when you are in a tech lead position.  Making one of your mechanics completely useless in the situation where you are playing well is an odd game design at best.  It's a pretty regular strategy to shoot for the tech lead.  So why would you then want to penalize that playstyle by letting everyone who doesn't tech trade on the cheap?

It's a balancing mechanism.   If you are ahead in tech, wouldn't intelligent beings think again about trading more tech to you?   Similar to many situations in other 4x games, such as the warmonger penalty in Civ 5.   The increase in research cost of techs as you acquire more (as in Civ series) tends in this direction also.

I tend to agree with Franco fx.   One doesn't need to check more than every several turns, and with a little bit of balancing of tech costs (especially tech valuation by the AI) I think things will  be fine.

What do I want in a 4x?  Lots and lots of choices, which have more or less complex, interacting positives and negatives.  Tech trading provides another powerful choice problem.   Buy a tech or a new colony ship or a factory or save the money or try to trade for it or...   Of course the annoying thing is that the AI will trade also.  It's another issue --- if I trade a tech, will it be passed around to the other AI, and will that hurt too much?

Tech brokering, on the other hand, I am not so sure about (selling or trading techs you haven't researched).

Let's assume it's crushingly penalizing to trade tech.  You get 1 tech for every 3 of yours that you trade away.  If there's three other players, you are now doubling your tech points by trading vs not doing so (you're doubling those three opponents techs as well).  If there are more than three players, you must participate in the tech trade game or get destroyed by the AIs that do.

Also, how much more micro intensive has that become?  Do I now have three techs I can trade away with any of my allies?  No?  How can I get a tech they don't have?  What do they have?  Oh they have these 20 techs each...  

It's easy enough to turn tech brokering off.  But I do not think it's possible to balance the game across different numbers of players with the feature on as it currently is.

Well i wouldn't want eliminate tech trading. Maybe component trading an idea. I'm sure stardock knows how to make untradable techs. I disagree about balancing more players, you could make techs worth more,  or are harder to research. I like  diplomacy. Even though there are 130 major races there are only 9 types of tech trees, so this will probsbly br bslanced by modders. You could mske some untradable. You may need bigger trees for nore race mods.