Amsterdam, the city with more bikes than people, has run out of bike parking space. That's why traditional cycle rental schemes aren't a good fit for the city: they just add more bikes to an already creaking cycle infrastructure.
It's also why Cycleswap is a good fit. The scheme works a little like Airbnb, only with two bikes instead of beds: you list your own bike and a price to use it for a day. Then you can rent out it out to a visitor, or someone who's bike has broken, or, well, anyone else who fancies it.
The site, which was founded by a group of students, has its own messaging function which puts hirers and hirees in contact with one another once payment has been received. Once the bike is rented, it's the renter's responsibility: they're liable in case of damage or loss, and would be required to compensate the owner for the cost of repair or replacement. On the Cycleswap website, it notes that the company can act as a "mediating party" if there's any dispute.
Here's an example listing on the website:
Just as with the peer-to-peer room rental site, Cycleshare has the added benefit of bringing visitors into contact with a local, who could recommend activities or routes through the city. From the company's website:
Cycleswap aims to connect Amsterdam's local bike owners to visitors, tourists and backpackers who seek to discover the city's beauty in a cheap and convenient fashion....Through Cycleswap you can rent a bicycle near your residence, guesthouse or hostel, at an affordable price, while being offered the opportunity to interact with Amsterdam's local community.
It could also help bring down the numbers of bikes before the entire city sinks under the weight of them.