Livejournal, to me, was a fusion of three things: a simple HTML editor (aka posts) + a time-sorted view and access controls + discoverability through your network.

The things that made it different than Facebook were (1) that they didn't screw around with your feed (it was your friends' posts, sorted by date), (2) that discoverability and networking was user intentional and exploratory (pull, rather than suggested / push), & (3) access controls were simple, understandable, and obeyed user intent.