Ask HN: When to get customers' billing info?

I'm working on the billing system of a new startup, and I'm trying to think through the plusses and minuses of when to get the credit card info from the customers.

I know that some shops (37signals) get the credit card up front, but say "we'll give you 30 days to cancel, and we won't charge you until the end of that time." This method actually bothers me, as it seems to spin "counting on you not remembering to cancel" as "doing you a favor, so you don't have to get out your credit card to actually sign up down the road." But maybe I'm being overly sensitive on that?

Have you tried multiple approaches? Has anyone done A/B testing on signup flows? I'd love anything you have ... anecdotes, data, whatever.

If it matters, the startup I'm working on at the moment has a freemium model, with a free (but feature-limited) version, and a paid (or multiple tiers of paid) version. The market is freelancers, self-employed people, and, to some extent, small businesses.