How do I delete this?

[SongCloud]

Unfortunately anything that you publicly post on the internet is fair game and can be re-posted anywhere as long as it is not against the Terms of Service of the site or service where you originally posted the content. Because all regular posts on Twitter are public and searchable from their main page, favstar.fm is able to repost them if they want to. You can try to contact them directly and submit a request for removal, but they are under no obligations to do so.

Always remember - Don't post anything on the internet that you wouldn't want broadcast all over the world or shouted from the mountaintops.