Yes, I agree with the changes, it will stop a good deal of the senseless pot throwing, which i see happen far too often.
Now for those who are inclined to argue against such changes, for whatever reason, perhaps you should take a closer look at the situation.
First off, if I'm not mistaken, somone mentioned earlier that you cannot cast area of affect spells in town to begin with, so there really is no issue there. Second, BS/EV not being caused to backfire was not a bug, it was OSI listening to people bitch about "oh no my 5 EVs turned around and killed me after owning the shit outta that guy", the creatures are CHAOTIC, or in layman's terms, they see no one as ally or as enemy but as a possible target. Third, explosion potions are not magical. Unless you want to code in a spicific, algoritmically complex addition that allows you to create magical potions at an additional mana and reagent cost with minimum magery reuirement behind it, explosion potions will continue to be non-magical. When you throw the potion, and it lands on the ground, it dosent know where to go, it has no "l33t tracking explosion" ability, it just goes off and hits whoever is within the blast range, including innocent players.
Now for anyone using these area of affect spells outside town, there is still an explanation to the situation.
With fields, dont cast them if you know there can be a problem, simple as that. If your near guards, you need to be aware of that fact and act accordingly, and dont cast a field you arent prepared to face the consequences of the assault. Taking on a house of reds isnt supposed to be find and dandy easy work, especailly when they are entreanched in a house. Oh, and dont walk into your own fields, or the fields of your party members if you choose to use them, thats just plain incompitence on your part if you blindly walk in to the field. Now for spells such as EQ/MS/CL, the problem which is being fixed is the balance issue of risk vs. reward. Think about this, as a mage you have the distinct advantage of being able to strike from a long range, while all fighters, archers excepted, need to be next to you to actually do damage. The drawback? You need mana to actually cast your spell while, albeit i do need stamina to swing mine, I do not need to actually use up my supply of stamina to continue to swing. Risk vs reward. For spells such as EV's and BS, you are able to literally summon a creature from nothingness to partake in melee combat, while still retaining the ability to stand back and cast. However, once the EV has either lost or killed its target, this powerful melee monster (that essentially gives the mage melee damage where he would have had none in the first place), has the chance of turning around and attacking its caster because of its chaotic nature. Risk vs. reward. Lastly, for spells like EQ/MS/CL this fix will rebalance the spells into proper use. If you use a spell like MS for example, like any other spell, it has the same risk vs. reward of range vs. mana cost. But the important part that is missing from the spell is area of affect damage vs consequences to those around you who are not an enemy. MS dosent require a direct target. All you need to do is strike in the general area of where you want to attack. For that ability to give an indirect target and STILL maintain the ability to hit a good deal more than one person, you have to deal with the risk of possibly striking somone who is not an enemy with your indirect attack. The same can be said about EQ and CL, if you dont have to directly target to get the damage done, then you have to risk the fact that because of the ability to indirectly target, you might in fact hit an unintended target with that attack. Risk vs. reward.
Pvp, particularly group pvp, is a complicated matter, you cannot just decide that since there are 20 mages and that you can all cast EQ, to go walk in and do 20 EQ's to kill an enemy, where is the risk involved? This kind of change will force intelligent thought into pvp, making it much more fun, and difficult.