Tempelton: How about letting us see all the questions on one page, instead of displaying one or two at a time?
HappyPunkPotato: Probably because some surveys dynamically change the questions based on previous answers, like how the answer to the question about using Galaxy determines if you get asked any more questions about Galaxy.
more likely about commitment. if a user see all the questions on one page, it looks enormous, and they will not start the survey. But when there are only 2-3 questions on a page it seem much smaller and the user starts ticking off. When they have reached a couple of pages in, they think "well, I have answerd so many questions now, so may as well finish". It is an old trick with anything that requiers commitment - start small, and then increase. Same with types of questions, start with easy questions and leave the harder ones to the last. Get people commitet.