I would quite like to see this feature added myself. And if we're asking in the wrong place, please let us know where else to make the request.
The Last.FM app on the Xbox 360 scrobbles (as it should, since it's Last.FM) - but the "Xbox Music" app for Windows 8 can't interact with the Last.FM Scrobbler. Here's hoping someone at Microsoft can reach out to and work with someone at Last.FM. It's been a great relationship so far on Xbox 360 and Windows Phone.