Whether you warned users of this change or not, to me, that isn't the problem. The issue is that they are stealth ads. As jacques mentioned, and the screenshot

Whether you warned users of this change or not, to me, that isn't the problem. The issue is that they are stealth ads. As jacques mentioned, and the screenshot shows, the ads look like they are personal recommendations by jacques, and this is what is quite sneaky/crappy about this whole change. If you went the route of using other language like sponsored ads, I think you were in the right, it's your service and you can change it, but this is indeed quite sneaky. It's like me going on tv and saying Bill Gates, Steve Jobs and Michael Jordan recommend my app. It's a lie.