Home holiday lets company Airbnb have been accused in Amsterdam and New York of facilitating illegal hotels. But why are so many people willing to open their doors to strangers, or indeed to stay with them?
Don't accept sweets from strangers has been a familiar parental mantra for generations, but people seem increasingly happy to stay with someone they don't know.
Airbnb is a website matching up homeowners with tourists and backpackers wanting a place to stay. Set up in 2008, it's one of a wave of sites - like Wimdu, and Homestay - making money out of those seeking a bargain. The firm says it has listings in more than 35,000 cities in 192 countries.
They do cover the luxury end of the market, but many of the customers of sites like Airbnb are trying to economise. Many indeed are backpackers travelling on a shoestring.
Taking a spare room in someone's stunning flat overlooking the Eiffel Tower usually works out a lot cheaper than a room in a stunning hotel overlooking the Eiffel Tower.
There's a catch of course.
These websites rely on customers and hosts overcoming their fear of strangers.
Many of the lets on sites like Airbnb are whole flats, where the tourist stays surrounded by someone else's stuff, but with the run of the place.
But it is also very common to get spare rooms in flats or houses where the owner actually lives. Tourists share with somebody they know nothing about. The owner allows complete strangers into his home.
