I didn't see anything in the link that said it would be opt in. He had said it would be opt out in the past. Opt out is the only way these things work. If it's opt in then just give us a white list option.
As a matter of fact, from your link... "For people who purchased the app and are now furious about his recent decision: simply disable it once this update to his app lands. You aren't being forced to acknowledge any ads as being acceptable."
The app update will come with this option turned on. It's on the user to opt out. Many users get their app updates automatically. Many users don't know enough to go to settings and opt out.
People are upset because they paid for an app whose sole purpose was to block ads. The developer promoted and advertised it as such. Said developer makes a bunch of money then turns around and accepts more money from advertisers to opt the users in to viewing ads. This is why people feel cheated.
This part.
Firstly - This will not be forced on anyone. It will be an entirely optional feature that will be described and presented clearly within the app before it is activated and that you can turn on/off at will. It will not be silently/secretly pushed out to everyone. I will to make sure that everyone is fully aware of how this feature works before it's enabled.
I say we give him a chance. I am not affiliated with the developer of Crystal in any way. I don't make a cent from defending him, nor do I have any form of stake. I am simply a very satisfied user of Crystal. I admit that I was one of the beta testers, and I don't know him in real life at all. However, he comes across as a pretty nice guy, and I feel it is only fair that we wait for this policy to roll out, observe how it is implemented, then lambast him if we feel he deserves it.
I agree with him to an extent. Ad-blocking should be viewed as the means to an end, not an end in itself. For now, we block ads not because we are fighting for a future with no ads. It's just that at the moment, ads have gotten out of hand, and ad-blocking is pretty the only way we can get the guilty parties to take notice and sit down at the table to negotiate with us.
I don't mind some ads, provided they are reasonable. I would like my favourite sites to stay financially healthy as well, just that on mobile, there is no way to weed out the bad ads while allowing only the lighter, less disruptive ones through (whitelisting a site doesn't count). I think what the developer is doing here is fair and reasonable.