World of Warcraft, for the first six months of its life, had no institutionalized player-versus-player combat. You could PVP, but you didn't go to battlegrounds to do it, and you didn't gain anything material by doing it. It just happened. Patch 1.4 came along and introduced the honor system, wherein you earned points toward ranking up in your faction and earning a title. During all of that time, the one place to go for all of your PVP needs was the Hillsbrad Foothills. There was a constant ebb and flow of battle between Southshore (R.I.P.) and Tarren Mill. Patch 1.5 did ... interesting things to that conflict.
The implementation of battlegrounds was a long-awaited feature, but as with all things in the early days of the game, things were hardly perfect on day one. You had to physically visit battleground portals to queue for a battle back then. The locations marked above in the patch notes? You had to actually be there to queue. Warsong Gulch players all huddled around their faction's instance portal dueling for countless hours. Occasionally, they snuck over into the other faction's zone to gank duelists. Alterac Valley players were still concentrated in Hillsbrad Foothills and continued to fuel the epic Southshore/Tarren Mill battle.
Dishonor, which you were slammed with if you killed a "civilian" NPC, proved to be a huge thorn in players' sides. Due to the chaotic, frantic nature of WoW PVP and how NPC aggro worked, you simply couldn't raid towns or cities without losing honor. The Hillsbrad battle was actually very dear to people. It was a popular, accepted activity. If you didn't want to lose honor, you simply couldn't do it anymore.
Rather than give it up, an interesting thing happened: Players took dishonor as a point of pride. Rather than PVPing only for the prestige, glory, and honor points, players said Screw that! and continued on doing what they'd always done, even if it was damaging to them and kept their honor bottomed out at 0. Because it was fun. To have no honor was, in fact, considered honorable.
Players who didn't go that route did not have much fun trying to participate in world PVP anymore. If you were a player who wanted honor to progress your character and advance through the ranks, you couldn't join world PVP raids. You had to run battlegrounds exclusively and make sure you completely trusted those you were partied with elsewhere. Even if you didn't kill a dishonorable target but someone you were partied with did, you still got nailed with the penalty. It wasn't uncommon for someone to lose hours and hours of hard work in battlegrounds in just seconds because a player they were grouped with decided to slaughter a few civilians while traveling between quests.
Future patches made it easier to tell which NPCs were civilians and which were not, but it didn't really help. The "honored dishonored" movement died out as well, as players realized that the dishonor system probably wasn't going anywhere and they'd like to progress their characters eventually. The war between Southshore and Tarren Mill largely dispersed, as more and more players grew terrified of being punished for participating in the wrong type of PVP combat. However, the dishonor system was eventually removed, and the battle for Hillsbrad resumed.
A side note: For those of you that haven't been around since vanilla WoW, when you hear old school Alliance players complain about losing Southshore in Cataclysm, it's not because they don't want the Horde to have zones to themselves, and it's not because we feel the Horde/Alliance zone ratio is improperly balanced. It's because we fought a war for that zone for over five years, and Blizzard decided we lost.
Innkeeper meeting stones
As you've seen previously (and will continue to see as we look at future patches), Blizzard made numerous attempts to construct a Dungeon Finder feature in the earliest years of the game. Each and every one until the implementation of the Dungeon Finder we know today was a complete and utter failure.
The first implementation required you to go to the meeting stone outside of the dungeon you wanted to run and queue up for it. I'm sure some people used that, but I don't know anybody who did. And if you're going to the stone, why not just type directly to the other people standing around it? In patch 1.5, you didn't need to go to the stone itself anymore. You could queue up for the dungeon you wanted from innkeepers. Of course, that didn't help at all.
Queueing for those dungeons didn't portal you to the dungeon when you got a group, so if you queued for Razorfen Kraul as an Alliance player, you still had to run clear across the world to get to the instance portal if you were placed in a group. Would you get a group? Who knew? Cross-realm dungeons didn't exist, so the pool of potential party members was quite small. So if you couldn't be sure you would get a group, and you still had to travel across the world to the instance on foot, and you didn't know how long you would be queued so you couldn't go questing while you waited and simply had to sit around the innkeeper ... what was the point? There wasn't one. I won't say nobody use the feature, but I will say very few people used the feature. It was more effective to spam Orgrimmar or Ironforge general chat to find a group.
Building on Molten Core
Patch 1.5 was another example of how vanilla WoW's raid scene didn't try to deprecate its own content. Molten Core and Onyxia's Lair had been the only raid content for six months. That was fine, because even six months in, not many people were into the raid game yet. Rather than just set it and forget it and move on to the next big thing, Blizzard continued to build on available content. It fixed weak itemization in places, finished item sets it hadn't had a chance to finish before the game went live, and fully implemented the Thorium Brotherhood. The Brotherhood exchanged Molten Core crafting materials for reputation. The reputation would earn you crafting patterns, which you then used against later MC bosses and, once patch 1.6 rolled around, Blackwing Lair bosses.
Yes, many of those things probably came around as a result of Blizzard's launching World of Warcraft with a completely unfinished and untested endgame, but it was still pretty cool to continuously get little pieces of content to spice up the raid, rather than getting it all in one big lump.