I don't understand why people get all bent out of shape when software they use gets shut down. At the end of the day, it's just one app. They're are plenty of other options for email clients, and god knows better ones will come out in the future. People act as if something close to them is going away forever. It's just an email client and you can still use it, it just won't be actively updated.
I also don't understand the impetus behind blaming Google or Facebook and treating it as if they are antagonizing you as a user. They made an offer and the developers accepted it knowing they would not be able to develop their app any more. This course of events is one that the developers actively chose. Frankly, I think it's great that these guys are getting acquired. They worked hard, caught the attention of a big company and were rewarded handsomely. After all, that's why they developed the app in the first place: to make money. There's absolutely no warrant for you to expect that the developers put their lives on hold so that you can have a piece of software.
As for Instapaper, I think that Marco is disconnected. If he is in a position where he has enough money so as to be able to ignore offers for his app and instead run a lifestyle business, fine. I also think that part of his attitude towards a buyout comes from the fact that, despite that he denies it and refers to it in jest, Marco is actually fairly rich. He was one of the earliest employees at Tumblr, a company now worth ~800m. That means that even the most minimal equity would give him a net worth in the millions. That's great for Marco. But I'd imagine that very few people are in his place. A lot of app developers probably dream of being acquired. Who can blame them? Everyone wants money.
So, although Marco has enough money where he can basically ignore the need to sell, most app developers don't. The Sparrow guys obviously didn't.