While I can agree with both points, I think it's beyond reasonable for anyone to think Blizzard would ban you for acting out a readily available game mechanic. Even if we were to assume that Blizzard is against the idea of using "Zolo like encounters" for boosting in this manner, Blizzard, as a company would not want to assume that all players, from this day to the end of days, would know that they even Hot Fixed Zolo. Until the day Blizzard makes the blanket rule "You may not use summoned creatures during an encounter to gain endless experience without moving." then there is nothing that makes it an exploit, or against the rule.

Intended or not this is a function of the game. In all reality, this is no different then a paladin running into the SM Cath, smacking the last boss in the face, then running back quickly to the door, and killing every mob in the zone in less then a minute. The fact is this was a known game mechanic. A party of 5 could have killed skeletons that Zolo summoned until their fingers were numb from playing if they so desired, long before a person used it to boost characters. Even still you can do that. Blizzard attempts to discourage things, not ban them, as such they will most likely continue to discourage more "Zolo like encounters" as well as further continue to discourage boosting in general.

I think we have to come to the realization that this isn't a stand by Blizzard against using encounters like Zolo to your advantage. This is a stand by Blizzard to attempt to further discourage boosting. Boosting is not an intended part of any game to the best of my knowledge. Blizzard has been kind enough not to make it so it's not impossible to boost, just discouraged it. They could easily just make it so any group with a party member X+ level's higher, causes the group to receive next to no XP, and suddenly boosting is over. No one is going to boost a party if they get 3 XP a kill. We should take this for what it is, it's Blizzard tweaking the game so that people have to work to earn their levels, rather then quickly rush through them, not make a policy statement.

**Edit** I'm adding to this because I feel it came out not saying exactly what I wanted. I need to learn brevity.

In no way do I want to sound like I support the use of this type of encounter. I believe that common sense and logic should have said this wasn't an intelligent thing to do, but I stand by it not being an exploit. Blizzard (And any other company) keep their EULA somewhat vague and open to interpretation for the same reason the Constitution is sometimes vague and open to interpretation. Because things change. Blizzard, just like anyone else, can not predict the future. They cannot predict what new and interesting ways people will find to do things, or to break the rules. By leaving the EULA vague something such as the Zolo encounter can just as easily be banned for, as hot fixed. This isn't to say Blizzard would, it's bad business to ban for something 'You' failed to account for, so they attempt to avoid it at all costs. Had the Zolo encounter somehow effected the rest of the world (Say all the skeletons dropped loot, and suddenly you just rained the Auction house with items from it) their decision may have been different. We don't know, we aren't Blizzard, and as such cannot speak for them. When you signed the EULA, you put yourself into a contract, that has only one exit. Quitting the game. If you did not agree with this contract you were offered a refund, their decisions will be final. Your free to break this contract, so long as your willing to pay the penalty (Being banned).

With all this being said, I've put together a very simple flow chart that I believe illustrates how to approach this type of situation.