ckaspar makes a point that is important in my daily commute. I have two right turn lanes I need to traverse and I do both of them differently. The difference is because what is on the other side of the intersection.

The one where I stay towards the side instead of taking the straight lane has a wide shoulder/lane on the other side of the intersection that [typically] happens to last long enough for all the cars that were waiting for the green light to pass me before a long narrow bridge comes up (where I do take the lane because it is narrow and I make a left just after it. This way the cars aren't stuck behind me and because of the wide road before the bridge, I'm not held up either. The down side to this approach is if there are alot more cars then normal, I need to go slower before the bridge to let everyone pass, but so far it always has worked out. If it doesn't, my backup plan is to act like the mountain bikers (and many others) and ride the sidewalk over the bridge. (Legal here, and almost never any pedestrians)

The other one has no right shoulder on the other side of the intersection and the lane isn't all that wide on the other side. It also has two lanes in my travel direction. In that case I take the lane.