Apart from the fact that this breaks open, and is the dumbest thing a player can do to avoid getting ganked (hurr, durr, just go to solo if you care that much, don't completely mess up the already bad instancing mechanics for TRUE open players), I don't think it works mechanically as you state it does. It was recently adjusted so that blocks override friends, was my understanding, I don't know which is true, but I do know that all kinds of crappery happen whenever you're around someone with a 'heavy' block list, so it may be worth getting a confirmation on that from someone at FD before stating that doing this won't mess up instancing with friends and randoms.
If you need an example of just how dumb this is, picture this... I'm flying in open, I enter deciat, I see lots of players, one interdicts me, I escape, I block that player. Now, that player is back in his instance in open, playing with, you know, other players who also want to play with other players, while you, who just blocked one person in the instance, are now going to be playing alone. In the worst case, you get back into supercruise first, and you are now with all the other gankers, while the ganker you just blocked can no longer get into the instance with the other players, cos you're in it and you blocked them. That's what I call griefing, not being shot at in OPEN in a spaceship game. Alternatively, you may be put into a smaller instance with fewer players, where again someone will likely try to gank you, but spear are in the instance containing players you just blocked, so you don't even see them, let alone get help from them. Then one day you'll be playing with your friends and all will be going great and then suddenly you'll get separated and be unable to instance together cos someone has someone on their block lists, it's literally an absolute crap show. Friends tell friends to CLEAR their block lists to help everyone instance better, and deal with ganking in a more appropiate and less selfish way (such as logging into PG or solo when they want to avoid playing the game with others).
So folks, if you want to avoid gankers, do the honorable thing and go to solo, don't abuse the block feature which is intended for people who are actually HARRASSING you, not just playing the game. If someone is following you around in the game abusing you and doing real griefing stuff, then obviously, block and report them, then unblock them some time later (you can always block them again if necessary. This keeps the wheels turning smoothly for everyone. Thanks so much.
what El Huevo says 
