Of course he isn't interested in promoting competition for other business. I'm not saying that he has to do so, it is his business. But I imagine content creators aren't interested in helping to pay Marco's salary via providing content for Instapaper, yet Marco doesn't ask them. There is a clear double standard: if it is your content, it is mine to use unless you go well out of your way to say otherwise. If it is my content, hands off, bub.

I'd be more impressed if he did allow sharing to competitors and let Instapaper win on quality, not a hard coded restriction. It would show a remarkable faith in his product.