I've never actually heard anyone mention couchsurfing as means of going on vacation... I don't even know if there is a place online that offers such a service, I'd have to check
However, I did find several people who are willing to rent their own rooms to tourists.
They are listed on various websites that people use to look for accommodation. When I search for accommodation, I don't use a lot of parameters, except for the dates (of the check in and check out) and the region, so I can find as many options as possible. I was surprised to see many people actually rent a room of their own house, at a cheap price too, for tourists who wish to visit various cities.
But these people are doing this for quite a while and, something tells me they pay taxes and everything, because renting your bed sounds like a business idea to me
So, it's safe! And much cheaper than a hotel too.