I disagree that your service was free. It sounds like the cost to users is receiving unwanted emails about other "freemium" sites you run. This is one reason I

I disagree that your service was free. It sounds like the cost to users is receiving unwanted emails about other "freemium" sites you run. This is one reason I prefer paying. If I'm paying I feel reasonably convinced I won't be annoyed in the future. But if I'm paying and still receive unwanted emails? Loss of a customer.