I always found this interesting because surely no matter what effort you go through to prevent yourself from providing your service to EU citizens, you're probably going to collect enough information to be subjected to GDPR during the period where you did not remotely know a set of users were EU citizens. (e.g., those residing overseas, traveling, etc)

And then -- what if you finally have confirmation? You were attempting to avoid it, but now you cannot. If your attempt is to avoid it at all costs, you're effectively required to validate whether users are EU citizens much earlier in the process than before GDPR, which means GDPR already has had a big impact despite efforts to avoid its umbrella.