Remember the huge scourge invasion that accompanied the roll-out of patch 1.11? After a few weeks of undead-slaughtering fun, the scourge invasion points across Azeroth vanished - whether your server had finished the invasion event or not. The "end" of this event was somewhat disappointing, as it occurred without any fanfare, and left me with a heck of a lot of now useless necrotic runes in the bank. However, there's now some suggestion from Blizzard that this invasion won't be a one-time event - though as to how often the scourge may become restless and attempt to invade Azeroth, no one yet knows.
Like the invasion or not, it was an excellent way to rack up Argent Dawn reputation, and the rewards (consecrated sharpening stones, blessed wizard oil, +damage versus undead armor), while situational, were useful. And, while I'm glad the invasion isn't a permanent thing, I think having it back on some regular basis will make for an entertaining diversion.