Motivation

So, for group content in MMOs, you have to have a clear goal.  The question always boils down to "why am I here?"

In Star Trek Online, I'm generally satisfied with a simple "to blow up the bad guys."  Not asking for much there.
With World of Warcraft, I'll settle for "it's pretty here, the fights are fun, and I can smash stuff."

With Star Wars: The Old Republic, though, you have to really motivate the experience.  When you spend so much effort on a game establishing it as a story-driven MMO, you need to have a legitimate reason for grouping up to tackle a task, and for making the call to action appealing to each player.

I spent some time yesterday in the group finder tool, just hammering out flashpoints and thinking about the content I was playing through.
I'm usually pretty impressed with the amount of effort put into making the world look fantastic in these small samples of group content.  Several times, I'd think it was more appropriate to just toss the whole thing into a generic warehouse/factory/cave and call time, but they went ahead and went all-in with the cosmetics.  I promise, I have a point for this.

The question goes back to "why am I here?"  Level/area designers can usually tell the stories with set pieces and decorations in the setting, effectively establishing a tone and guiding players along without saying a single word.  It's game design 101.  There's a whole chapter on it in the introduction to game design text I used to have.

I like how varied the means for establishing motivation vary from game to game.  In City of Heroes, you were a hero and the city was full of bad guys.  You go down the street, you see crime, you stop it.  Bam.  With STO, space is huge and empty, so if you were in an area and there were things...you go to them and apply torpedoes or scans as necessary.  WoW?  Kill all the things, loot, check map for directions to next objective, repeat.  In SWTOR, you have a conversation, then you go and you do, then you have another conversation.

With tabletop games, such as Dungeons and Dragons, the motivation can be a lot harder to come by, and varies greatly from Dungeon Master to Dungeon Master.  In these settings, you're telling a story that can change at a moment's notice, entirely because players choose to behave differently.  Then, as a story teller and DM, you have to find a way to guide players back to the plan, or be ready to motivate them toward a new goal.

The advantage that games have over most other media is that the player is directly involved.  We, as players, have to buy into a world and reasons for behaving in a certain way...and the puppet-masters have to should try to pull the strings in a way that is gentle and efficient.  It's an art, and I really like seeing how it's done.