Back in the day all area of effect spells would hit everyone within the area. Blade spirits and energy vortex's would also attack anyone. I kind of miss it because that was when those high level spells were very effective. One EQ would really hurt. I have mixed feelings about going back to that. There are good reasons and bad reasons, can't make up my mind.
Yeah, UO had "Friendly Fire" a long time ago. AoE spells like Meteor Swarm, Chain Lightning, Mass Curse, and EQ would damage anyone in the area, including guildies/party members.
WWs weren't used alot in Fel or Tram for a long time because they had the nasty tendency of casting Mass Curse (The only pet ever capable of casting an AoE Spell in UO), often hitting their owner with it, then turning around and chomping the tamer in 3 bites. Only time you really saw a WW being used, was by a unguilded tamer in Tram, Mass Curse couldn't hit blues in Tram, unless they were guildies. They later got rid of Mass Curse from WWs.
Field spells would also damage anyone that stood in them, we had a term for people who liked to run into your field spells to turn you grey, "Hoppers".
Summons like BS and EV would also go after anyone, even their master. BS tended to go after Warriors first, and EVs tended to go after Mages first. Can't even begin to count how many times i'd seen a Mage killed by his own EV, when he attempted to summon the EV on a Warrior in Buc's Den. BS and EVs were NASTY back then too, BS could do Greater Poison with it's hit, and EVs could do DP and Curse with their hit.