Ever used it?

I recently became a host; I've now hosted two different people for three nights total. Next week I have one more person, staying for five days. I have other requests coming in but I want more space to myself and they have no reviews so I have declined them. Legally, I shouldn't be doing this because I'm only renting. But all formal accommodation in my (seaside, famous surfing) town is booked out until February, so there is so much demand, it's unbelievably lucrative. I'm charging NZ$30 a night for just a bed in a room with a desk that otherwise just stores some empty boxes and occasionally sleeps friends.

My first guest was a full-stack JavaScript developer from Prague, Czech Republic. His English was terrible, or at least he had a major problem with vocabulary and trouble understanding my accent. However I did manage to get some conversation out of him, and we bonded over beer and Portal 2. Portal took a lot of pointing, but we managed over 40 levels together. I'm living by myself for two months, so it was kind of like renting a friend, except he was paying me. He was only going to stay one night, but ended up staying two as the repairs on his van took longer than planned.

My second guest was a (frankly, very attractive) 21-year old student from a small alpine village in southern Germany. She thought my town (~3,000 people) was big. She came to New Zealand because she had just started a fashion course in Berlin, when she was told she had a tennis-ball sized tumour near her ovaries. Apparently they got it out easily and won't have any repercussions, but she delayed starting her studies. She had had a terrible time so far in my country. Her first week here, spent WWOOFing, saw her teamed up with a German guy who made her do all the difficult tasks, while laughing at her and eating all her food. She was a very naïve person, I think. Her first night here, she had no accommodation planned and instead spent time in the centre of a city trying to find some. A man with an 8-year-old son appeared to help her, acting very friendly, but asking weird questions (in her words: "Are you a clean person?"... she thought that meant, "Stay at my house, just clean my kitchen to repay me"). He convinced her to come to his house and sleep on his couch. When she got there, she realised (rather late) that something was way off. Apparently there were old motors all around the front lawn, the floor of his house was covered in old food packaging, and the only bit of furniture was a mattress in a corner. The man got drunk, and she didn't know how to get out the situation. She thought she would be safe as long as the man's son was also in the room. So when he told his son to leave so he could "speak to her alone", she said she had to go the toilet, and grabbed her bag and escaped out of the bathroom window. Eventually she was helped by some students and slept on their couch (they were very nice, apparently). I've since filed all I heard with the police, but she couldn't tell me where any of it happened on a map. After all that, I didn't even want to make her pay, so I gave her back the cost of staying at my place.

Apart from her distressing story, she was very nice, with plans to attend the local surfing academy for two weeks, so I might she her around again.

So so far two rather different experiences. I think when/if I travel overseas, I'd like to use Airbnb, or some kind of couchsurfing app. I feel it's a good way to get cheap accommodation and a more authentic experience at the same time. What are your experiences with it?