The biggest problem IMHO with the APIs is inconsistency, for instance on the FB graph API on some calls it gives you a 302 redirect instead of returning JSON.

The biggest problem IMHO with the APIs is inconsistency, for instance on the FB graph API on some calls it gives you a 302 redirect instead of returning JSON. so instead of { image: "http://foo.com/image.jpg http://foo.com/image.jpg } you have to catch the Location header and write it into your object. Next up would be how to represent a date in JSON which seems to vary between an time_t cast to an "int" and a string in ISO-8601 format. Lets not even get started on XML and attributes vs. elements.