For background, I am a mathematics graduate student.
Now, it happens once in a while that I find an interesting conference/workshop which I would be happy to attend, but which I'm not sure about (for reasons which might appear later on, such as not enough funding, finding a better conference etc.).
Suppose that in case of acceptance, the organizers offer some travel/accommodation funding, and that enrollment closes a relatively long while before the conference takes place. Also, suppose that I am not offering to give a talk.
Is it inappropriate to enroll with the knowledge that there is a relatively big chance I won't be able to participate, and retract my enrollment after being accepted if I realize that I indeed can't go?
Does the answer change if I enroll at several conferences "just in case" and then go to one of them if I'm offered enough funding to cover my expenses?
Is there a point after which cancelling my participation is considered rude? What is the polite way to do it? Is it common, in your experience, that (student) participants cancel their participation after having been accepted?