I don't have any statistics to back up my answer, but I suspect that requiring a CC at signup will decrease your revenue. I know personally, I do not sign up for things that require my credit card. I blame gyms for this. It is the classic stereo type where you sign up and then forget to cancel. Time is very important, so I don't want to deal with having to cancel.
My webapp as a free trial (very little information required, username/pw) and a free demo (no information at all required.) My support costs are virtually 0 for trials and demos. In fact, any customer asking a support question ends up being a paying customer. They actually want to use the product. I want to maximize the number of prospects at the top of my sells funnel, so I reduce the barrier to trial to as little as possible.
If anyone has done an A/B test on this, I would like to know the results.