I love how you make sound like it's no big deal to have six people split on an expensive capital asset like real estate, all to get around an AirBnB law.
1. 6% house sales tax.
2. BAG registry contains all address registrations in incredible details. Public data. More available for a price.
I don't see why it being public would matter: the whole point is that this should be legal since the owner is only airbnbing it for 60 days.
Not trivial at all. Without even pausing to think, I could offhand list at least four different ways of writing my home address that would be impossible for AirBNB to automatically disambiguate from other (potentially) different residences, without actually visiting the building... but which would be perfectly unambiguous for a guest who actually visits.
Address verification is hard. Not impossible, but when you're operating in many cities and countries that have wildly different ways of organizing their addresses, it's not trivial at all.
Though I'm honestly not sure those are as comprehensive as certain other countries, as you mentioned. Germany has the Meldepflicht[2] for instance, which requires all residents to register their address with an Einwohnermeldeamt, and I'm pretty sure that's validated against a nationwide database. Granted, it's not granular enough pinpoint exact apartments (since apartments aren't generally numbered here), but still, I imagine that kind of thing would make it pretty difficult to bypass a law like Amsterdam's 60 day rule.
[1] https://www.usps.com/nationalpremieraccounts/manageprocessan...
AirBNB doesn't offer insurance - it offers a "guarantee", which is legally different in an important sense.
In any case, if you're looking to rent out your place full-time, you probably don't really care about AirBNB's guarantee anyway.
Therefore, Airbnb doesn't really verify addresses at all, and lets people bypass any system that relies on this. This happens in major markets where Airbnb has people on site too: A good chunk of listings in San Francisco's SoMa are doing this.
Thus, I have little faith that any system to prevent breaking local laws based on addresses will go anywhere unless Airbnb does a lot more work to verify the accuracy of listings.