Sure they are obviously free to do what ever they want with their products and maybe "pulling the rug under your feet" is a bit dramatic but it is true that they are pulling features left and right (not only Reader) that unless it is used by the 80% enough is under hard scrutiny. But if the top 20% which is also the people that are going to help you innovate are getting tired of getting used to a product working in a certain way and then it no longer does they will be wary of being too dependent on products from that company.