Understand they can do whatever the hell they like as you say. But I think the problem is in a way they're blackmailing their users. They're leveraging the fact that people are very unlikely to switch messaging platforms that they've invested in building a network in. It plays on our deepest instincts as social animals. No one wants to self exile themselves from their friendship group. Leveraging this instinct to grow your business is evil in my mind.

When I say evil I mean morally wrong.