In my opinion subscription services can be lucrative and valuable if you are able to start a venture that is of value to your target customer. You certainly need to spend a sufficient amount of time training your customer service department. Your site would need to be user friendly due to requesting subscriptions can quickly daunt the potential customer if they most go through lengthy questionnaires or profiles. Almost anything can possibly be converted to a subscription but in this economy it would be a great marketing tactic to have at least somethings of a value free of charge until you develop a reputation. I believe this trend will be short-lived because it generally seems the deployment of the site to be somewhat rapid due to limited requirements of customization due to similarities as far as web designing goes. The main concern would be the product and you most certainly would need more than one product in order to be able to compete.