Not really good enough. It's unacceptable to ask your customers to expose themselves to unlimited billing liability. This is one thing that Google gets right and yourselves and Amazon don't: the ability to set a budget.

I bet if I didn't pay my bill on time you'd cut me off pretty quick. Why not let me tell you how much I've got to spend ahead of time so there's no nasty surprises when I get back from vacation while some bot has been rampaging through my site?

Of think of it this way: today's offer is designed to get people using Rackspace by lowering barriers. You're hoping people will like it and stay, or be too lazy to move. Don't you think the potential of an unlimited bill is another significant barrier in people's minds? I bet you're losing sign-ups.