[anxx]

The "they" we are talking about are AirBnb employeees, not some random people. It's no different than giving a copy of your passport to the bank teller - in theory they could also use your info for bad purposes, but it's much less likely than a random person.

[calvinlough]

The "they" could be AirBnB employees, but it was probably a reference to hackers breaking in and copying those files from AirBnB servers. The fewer servers that have a scanned copy of your passport, the better.