This is a random thought from a few threads I've started, or posted on, or just read. Some Attractions like Indy, Splash, Space, Rodger Rabbit, and Jungle (when it has people in it) are fully immersive and really attempt to get you into the theme. Other attractions, most recently Nemo, offer little or no theming. So the first question is does the theme of the queue enhance or detract from the actual ride itself.
Now for those rides that do not have an enclosed queue that hides the line there is another question. Does a longer line entice more people to ride it? Meaning that if there is already a crowd more people think "Hey this must be good" and thereby make the line longer. OR Does a long line persuade people to keep walking? I have a feeling the responses will be different depending on how often you visit the park!