Leigh Dodds' recommendations for building user-centric services (I think Playr does most of these, and I'll add RDF feeds this week to complete the set):
- Don't try to do to much: do a few things and do them well.
- Make it easy to add data to the service. Bookmarklets, augmented with a small form, are the best way to handle this.
- Don't appropriate my data or restrict it's use: at the very least I should be able to get back what I put in. Ideally it should be augmented.
- Provide a REST style interface to export the data. This should use stable URIs (so I can rely on it) and it should not require manual intervention to export the data.
- Facilities to protect the data export are welcome, but should not be required. Doing so makes it harder to share data.
- Use RDF for the data formats, it's designed for integrating disparate types of data; failing that use XML so I can easily transform it.