1. I rented a place and was told that I could check-in whenever. When I got there, the key wasn't available and I wasn't able to contact the host. I was essentially just standing around for three hours waiting for Airbnb to respond. Apparently, you can contact them, but it's extremely difficult to call them if you're international unless you want to pay for roaming, which I doubt they would compensate you for, so I had to wait for case managers to reply to my email.
After fiddling around with my phone for a while, I managed to install Skype, sign up for some credits, and call them. It was resolved within an hour after that, but the non-savvy tech user would probably have a lot more trouble.
2. The second incident was when I went to an Airbnb and the electricity wasn't working, the roads were closed off for 3 blocks to the apartment due to construction. I paid for a week's stay, but I immediately left since this wasn't disclosed in the listing.
By the evening, I was fed up with the problems, so I left to another Airbnb. I contacted Airbnb, again through email support, since that was all they offer and they told me I could not get a refund since I was past their 24-hour cancellation policy. After going through numerous emails and case managers, I never received my money back based off of a technicality. Their response was that I should have contacted them immediately... but they don't make it easy to contact them.