I find that I can push the needles forward for a few rows without using the cast on comb, but there still needs to be some weights used, at least on the end needles.
Without the weights the stitches on those end needles will sometimes just jump off. If it is on the bulky machine it isn't always a problem as the stitches don't run really fast, but oh man, on the standard it's start over again.
I am not that fond of frogging. LOL