@nilesh @ainali If you try to distinguish between robots and humans like that, you're bound to block, say, the Tor users. Therefore, "retroactive" is the way to go.
Think of DRM: If you use Netflix in Google Chrome on Linux, you get a considerably worse quality for the same price because you can record your own screen and make a copy. But not on the Netflix app for Windows – it's inconvenient to some, but meant to protect something. Their shows still land on piracy sites within hours anyway. ~n