Hello Sindre
Last.fm already has an excellent library and API (http://www.last.fm/api) and there are some great plug-ins and extensions already out there for XBMC and Google Chrome, so why not integrate Last.fm to make Subsonic even better.
Please could you look at implement the following features:
1. Ability to add a Subsonic track to a Last.fm custom user playlist
2. "Love" a single Subsonic track which automatically updates loved tracks in a Last.fm account
3. Import a playlist that has been exported from a Last.fm account (In Last.FM you can export a playlist in two different formats).
4. When a track is playing in Subsonic and scrobbling to Last.fm include an option to display artist info, event info (if touring), similar artists with a play/preview option from the Last.fm website.
5. Import and configure Last.fm RSS feeds to each Subsonic user profile, for example "Recently Listened", "Top Tracks", "Top Artists", "Loved Tracks"
6. When clicking on a track list link within a Last.fm RSS feed/playlist Subsonic will play the music directly from the Subsonic library if it exists, if it doesn't exist then it will play via Last.fm.
7. Allow for multiple Last.fm scrobbler accounts in Subsonic (one for each Subsonic user profile)
8. Promote new album releases from artists found in the Subsonic library.
Below are a list of typical RSS feeds that I found in Last.fm that could easily be parsed and integrated within the Subsonic website.
Recently Listened Tracks: http://ws.audioscrobbler.com/1.0/user/mcUNKLE/recenttracks.rss
Loved tracks: http://ws.audioscrobbler.com/2.0/user/mcUNKLE/lovedtracks.rss
New Releases: http://ws.audioscrobbler.com/2.0/user/mcUNKLE/newreleases.rss
Free MP3's: http://ws.audioscrobbler.com/2.0/user/mcUNKLE/podcast.rss
Events: http://ws.audioscrobbler.com/1.0/user/mcUNKLE/eventsysrecs.rss
Recommended: http://ws.audioscrobbler.com/2.0/user/mcUNKLE/newreleases.rss?userecs=1
Top Artists Overall (There are also artists RSS feeds for: Last 7 Days, Last 3 Months, Last 6 Months, Last 12 Months) http://ws.audioscrobbler.com/2.0/user/mcUNKLE/topartists.xml
Top Tracks Overall (There are also track RSS feeds for: Last 7 Days, Last 3 Months, Last 6 Months, Last 12 Months) http://ws.audioscrobbler.com/2.0/user/mcUNKLE/toptracks.xml
Top Albums Overall (There are also track RSS feeds for: Last 7 Days, Last 3 Months, Last 6 Months, Last 12 Months) http://ws.audioscrobbler.com/2.0/user/mcUNKLE/topalbums.xml
Adding the video stream feature is great and all but let's not forget what Subsonic is mainly all about - music.
You'll get a big donation from me if these features are implemented.
Cheers!