Mullvad requires little data for creating an account. An account number is generated, eg 0522541830655744, and that's it. No email, no credit card info. So there is not much they can give to authorities when asked.
Mullvad says when confronted with a serach warrant they were able to convince the police that they have no customer data to give out..
Are there any other VPN operators with a similar concept? How do they operate? What's required for creating an account? How can you pay?