Doesn't work on the following sites:
- Spotify (Web Player): No Media Found
- Bandcamp: Access Denied
- Soundcloud: Access Denied
- YouTube: Access Denied
- Newgrounds (Flash game): No Media found

It does look like it's working properly the way it's supposed to, but it seems like the most popular media streaming sites simply do not play well with the way the extension is implemented. It would be a great add-on, if only it worked with these sites. Too bad.