The latest trend in e-commerce industry is the use of usage-based billing. Digital service businesses should be looking to integrate at least one method of usage-based billing in their business model in order to tap into new revenue streams and maintain customer satisfaction in this competitive environment. James Gagliardi (Vice President of Product and Innovation at Digital River) writes in his article link about two models businesses should consider – subscription and freemium:  http://digitalmarketingmagazine.co.uk/e-commerce-digital-marketing/the-recurring-revenue-revolution/1413