We have added some new collaboration features: It is now possible to easily invite all of your friends to a track (a friend is someone you follow and who also follows you). If you are feeling even more adventurous, you can also allow everyone in! To always keep you in charge of your track, new users can only join as long as you are active in the track. Opening up a session for all of your friends will also send out a notification to them.
These options can be found at the invite dialog in the app.
We also added a sidebar next to the newsfeed that (among other stuff) shows the currently active collaborations you can join.
Update #1: If you open up a track for everyone, it is always a good idea to use bookmarks frequently, so that you can revert changes you don't like.
Update #2: Owners and administrators of a track can now roll back changes done by other users (via the history panel on the right). Note that the keyboard shortcuts for undo / redo still concern your changes only. We also added an option to permanently ban a user from a track. This is done by simply removing them via the "get together" button.
Mini-Update #3: We have rewritten some parts of the network layer. Joining collaborations is now much faster.