It would be ok to lose signups from people who would not ever buy your product, but I don't think that's the case.

I for one, subscribe to a lot of SaaS but would never put in my CC number just for a trial.

And what about corporate customers? I think many subscribers can come from corporations where someone somewhere tried the product and liked it, and then made sure his company paid for it. If he had to enter his CC# before he could even try he would probably not do it.