The context is if someone using the cafe's internet infringes on copyright, the copyright holder needs to find whom to sue. That is not possible in a "type a random email address" mode.
It sounds like the latter, but the idea that I might soon be required to set up a "Sign in to Facebook to use cryptarch's free Wi-Fi" portal is pretty frightening. (Because, of course, just any identifier won't do!)
I used to live in a time where you could book a hotel without providing a valid ID.
Don't you already have to do this with most free wifi? A lot seem to offer a free 30 mins but more than that are you have to create an account.
The only problem is that many cafés / bars don't provide wifi, because they are afraid of providing wifi at all due to the "Störerhaftung" (a legal issue that exists almost nowhere except in Germany). Luckily, there's Freifunk and VPNs to the rescue.
Or you can also not allow torrent/etc through your Wifi service
If you have to disclose your identity in order to use free WiFi it pretty much kills free WiFi. The court seemed to understand that terminating the service was not an appropriate remedy, but then proceeded to shoot it in the back.