I never liked research trading in Civ4 (and prior versions) and I don't like RAs in Civ5. I especially don't like the "RA blocking scheme" where players sign a bunch of RAs, the research things they do not want picked just to 25% so they are not picked when RAs expire. RA's should be eliminated, but definitely RA blocking should be disabled as an exploit. If you look at what goes on in the Game of the Month competition, all the winning results revolve heavily on RAs and blocking pretty much no matter what the civilization, map type, or indicated victory method.
One could say that in Civ IV XOTM, all winning results revolve heavily on optimizing perfomance given a particular set of game rules and mechanics. And it is a human's ability to do that better than the AI that allows the human to win on levels where the AI gets bonuses. Skilled humans will always "exploit" the rules and mechanics better than the AI ...
So the question is at what point is an exploit of the rules and mechanics so undesirable as to be banned?
The "unintended loophole case" seems obvious. If the programming allows behavior that seems clearly contrary to the game concept (building multiple copies of wonders, or getting infinite techs from oracle in Civ IV for example), easy to make the case for banning it.
I guess the other category that might get banned are some of the "taking candy from a baby" exploits. Examples of this would be trading tech for gold, then pillaging the tech to kill the deal, rebuild and repeat. Using OB to walk up to a city and then declare war was another one in the old day, but now the magic of teleportation in the rules eliminated that.
So is tech blocking an unintended loophole? Well, it is not there because of what the programmers didn't do ... we have tech blocking because of what they did. They built an equation to esesntially prevent RA from giving you a tech you are already invested in. Maybe they overlooked that this could be used to block off entire branches of the tech tree. That could be "fixed" as much by adding more cross-links to the tech tree as much as by nerfing RA's.
Is tech blocking an aggregious "candy from a baby" issue? My guess is that the AI aren't programmed to do it, so maybe it is? But since the AI are so flush with cash at the high difficulties, and sign lots of RA's, maybe tech blocking is a necesary equalizer for the human trying to play peaceful on those levels?
Be interesting to know what the Frankenstein Group concluded about tech blocking in their testing (assuming that they did test it).
I find that it adds something to actively manage in the game ... which Civ V has been a bit short of compared to Civ IV IMO. In early versions of Civ V I often felt like a spectator in my own game, not a player. The more that the player has meaningful choices to make, and various futures to envision and decide between, the more fun the game is, I think. RA's and tech blocking each add extra layers of management to a game, which for some of us adds extra fun.
Not to mention that banning it will wreak havoc on the Civ V HOF tables (as will any new patch that substantially changes it)
dV