This Is My Jam.

Once a jam expires or is changed, it is listed at the bottom of your profile (or jam) page with the rest of your past jams. From there people will be able to view every jam you've previously posted, including the source link to the music. (This Is My Jam uses source websites like YouTube and Hype Machine for their music.) That way if, say, you really like one of your friend's jams, you can listen to it even after they change it.
Eternal jams allow you to (in a way) get around the expiration date: if you have an eternal jam, when your current song's seven days run up you're eternal jam will be put in its place until you return to update your profile with a new song. Picking an eternal jam is easy; simply select one of your previous jams in the drop-down bar at the bottom of the page. There it will stay (advertised as your eternal jam) until it is needed again.
There are also some really fun playlist options. You can play all the jams from people you follow; a custom playlist tailored by your friends can be entertaining. There's an option to play all the jams you've liked; so you know what you're getting into, and familiarity is always nice. And finally there's a playlist that's created from suggested people for you; This Is My Jam suggests people for you to follow based on musical similarities and mutual followers, and you can listen to all their stuff in one go.
All in all, this site is an amazing way to share music with your friends and find new tunes to rock to. With an ever-changing playlist and any number of genres, This Is My Jam is one of my favorite social media discoveries (right behind Twitter, of course). I've been hanging there for a while, and if you want you can pop by here to check out my jams. I encourage you to check this place out, and maybe even try it for yourself. You can link it with Twitter or Facebook, even make a separate account just for TIMJ. Whatever you do, I hope to see you there and hear some of your jams.