I think that cheating in an online environment is a real possibility. I was a TA for a professor in an online course and you can see that there are students working "collaboratively" on projects and exams by how they log in to take them. The ability to watch students in the online world is very powerful. It is an ethics thing.
I also one time had a professor accuse me of cheating by my score on turn it in. He did not understand the technology so it cuts both ways.
Doug