Instapaper probably was my first paid app when I got the iphone 4 3 years back. It has seen a tremendous growth over the past couple of years.It was a great product for a one person developer. Though Marco‘s decision comes up to me as a surprise the decision is good for the end users and for the product which is very appreciable.
If you are an Instapaper fan you would like to hear more of the reasoning in Marco’s own voice here