Somehow charging at trial signup doesn't _feel_ right to me. Even if you are able to charge once and then users ask you to cancel, this means they never would have paid if you had not asked for their card at the beginning. What use is revenue if customer isn't likely to have used the service or doesn't need it (but simply paid because you automatically billed them)?
However, as a way to weed out non-serious users, I can understand the rationale (but then again you would let go of publicity effect).
Great questions! The idea is not to charge them on day 1. The idea is to charge them on day 30, just like you do right now, but collect their CC (and revocable permission to charge it on day 30) on day 1.
You're not trying to get people to forget about the service and pay for one month then cancel. That's not a long-term success for the business. You're trying to extract a commitment to pay money because extracting a commitment to pay money automatically increases their perceived value of your service, their engagement with it, and their likelihood of paying for it.
Forcing the decision-point until when the trial is over will cause them to discount the value of their software because a) they've already consumed it or b) they haven't had time to look at it yet but have had time to totally forget your sales copy about it. You want the big decision point to come at their moment of maximum perceived desire for the software: when they've just come to your website with a headache and you've just told them you're selling aspirin, the magic cure for headaches. At that moment they burn with desire for aspirin, so get agreement in principle that if the aspirin cures their headache you get paid, rather than saying "Take this aspirin and then let's talk about how much you value not having headaches four weeks from now."
After you get people to make the decision, all of their future actions will tend to reinforce that they previously made the correct decision. (People hacking 101.)
Thought, someone else brought up a point that the person visiting the landing page might not be willing to use his/her credit card when trying to sign-up on a company's behalf. So, does it also boil down to the kind of market you are selling to (when the end-users are not independent decision makers)?
I don't know about most companies, but every single person who would have been in a position to buy software on the companies behalf could have easily pulled out their company credit card or the sheet of the paper that each department had with the credit card info on it and bought the software.
These companies ranged from 2 people to 400+ people. Most SaaS offerings are under $50, which seems to be something that most business people won't hesitate about spending money on and certainly wouldn't require someone to go to someone else to approve.
If this is the case in your company you're wasting a lot of time!
However, as a way to weed out non-serious users, I can understand the rationale (but then again you would let go of publicity effect).