Really depends on how you view your character.
Mine just wants to: Pick up cargo, fly it to another planet, unload the cargo, get paid for doing it, and spend as little time as possible doing datafiling for customs official.
Unfortunately, this moron called Rogun hired a gullible fool of a dock foreman, who hired a swindler that stole their cargo, and my ship. They stole my ship. My ship.
Skavak committed suicide when he went off in my ship, he just didn't realize it. I might have let the issue slide with Rogun if he had promptly apologized by delivering my ship, a big pile of credits, and Skavak's head in a bucket. Instead he blamed me for the actions of one of his employees. His employee, his organization, his responsibility, and he sends bounty hunters after me?
That motivation took me all the way through the end of chapter 2 of the storyline. It also explains a lot of the motivation leading up to chapter 3. Why did I work for dodgy characters? Well, as long as they were getting me at least one step closer to Skavak, and later Rogun, I really didn't care what their agenda was.
Chapter 3 was a bit of a letdown in some ways. The Voidwolf and his cronies were more paid work than personal vendetta, but it did make sense in terms of a transition from the class story to endgame FP, WZ, and Op content.
As far as light side/dark side my smuggler was 85 - 90% light. Dark side choices involved the removal of heads from Skavak and Rogun, and the occasional pragmatic elimination of Sith or Imperials in cases where it was clear that if you spared them you'd just wind up killing them some other time. If there was more actual smuggling, and avoiding taxes and paperwork counted as dark, then he might have been considerably more dark side.
I also didn't do the whole crime lord thing. Why would I want to have Rogun's treacherous, incompetent, slimeballs working for me? I have a competent (mostly) trustworthy crew already. Best of all, I don't have to pay any of them!
I kind of wish they had max level class quest lines though. IMO the class storylines are SWTOR's strongest feature and I'm not sure if I'll stick with the game once I run out of classes to level. Without them it's sort of like Burning Crusade era WoW with StarWars graphics pasted on top ( ok that's slightly harsh, but not far off the mark I think ).