Web APIs and mashups are not only of interest to the developer community. There are also research activities that look at how to improve various aspects of API design as well as services' and mashups' implementation and deployment. If you are interested in a cutting-edge research that may influence the future of Web APIs, then you should look at series of workshops on Web APIs and Service Mashups.
The xenon-canto API allows developers to access information on 8,244 bird species, including over 100,000 recordings of bird songs available so far. Over 20,000 recordings are added each year. However, they say this is a long-term project, with an estimated 2,000,000 recordings needed for a complete record. At current rates, recording them all would take over 140 years.