I would stay away from scotch tape. I don't know how it will act for sure on a fingerboard, but having experienced scotch tape residue on other surfaces, I don't think you would be happy.
If you feel the need to have fingerboard marks, I would check out that link that Ray posted of the other discussion and see what other methods of markers people have used.
True story about fingerboard markings: My college professor used the little 1/4" colored sticky dots. His habit was to walk up to me (or other students) while I was playing a piece and
WHAM! stick them on the fingerboard. Um, maybe that was a hint?
