That's funny. I glanced at the headline and then started writing my comment without reading your post.
I started writing about how annoying I found it when Optimizely started billing me after my free trial. Yes, I was using the service, but I hadn't made my mind up about. It's just an opportunity to help people trust you. Send them a reminder 24 hours before "we're going to charge you"...especially for a year of service. Come on!