Said trap would hit any former returning customer who saved the wifi password.

Not if you limit it to trap-only passwords you leaked yourself.

Perhaps would work better if you severely slow piggybackers down instead of outright blocking them. If they think your connection is just bad they won't know they need to escalate.

If you wanted your Wi-Fi to be for customers only then you'd use WPA2 Enterprise with unique per-user passwords, or at least change the static password every day.

You might want your WiFi to be for customers only, but not have any idea how or enough money to enforce it.

I might want a million dollars but have no idea how to earn it nor enough power to force everyone to give me their money.

Now give me my million dollars!

Let’s be real. You can’t have your cake and eat it too.

Requires a geek for a few hours and Ubiquiti network gear: https://cdn.arstechnica.net/wp-content/uploads/2018/06/1unif... (from https://arstechnica.com/information-technology/2018/07/enter...) Even integrates with Facebook WiFi to abstract away the auth systems (and further degrade privacy!)

I might want a pet unicorn too, then what?

Changing the password everyday is an acceptable compromise.

The password was changing everyday where I worked, with the daily password available on an intranet page, but then a few months ago a bunch of higher-ups were present in the office for a few days and wanted Wi-Fi access without having to type a new password each day, so the password rotation has been deactivated since

Well they chose convenience over security, which in this case is fair enough (it's public Wi-Fi to being with).

Another solution would've been to implement WPA2 Enterprise, where employees could have their own, permanent credentials while visitors get temporary ones.

Also I don't think you can access anything in the intranet on that Wi-Fi, it's entirely public, as you said.

Then you probably won't know enough to setup that trap.

Well, if I was a cafe owner worried about non-customers going nefarious things I would not be happy until IBM deploy a decentralised blockchain solution that anyone with a HTC phone hardware wallet can seamlessly sign in to with the task only taking thirty minutes or so.

Or maybe make it as easy as possible, never changing the password and thereby getting repeat trade. I am sure a firewall can be opted into with the ISP to make sure nobody is downloading ISIS kiddie porn, Trump tweets etc.

Wlan is usually not that strong to be reachable outside said coffeeshop. If you live near enough, you'll know the key anyway. (for the chance it does)