Group goals on user page by user defined categories
For example to group training related goals, books to read etc.
David MacIver commented
I like the competitive group goals idea.
I in *principle* like the cooperative group goals idea but I'm worried it might be a source of conflict. Having money on the line might work as a good motivator individually but I'd be worried that when a group fails they'd point to someone as being at fault for "not pulling their weight". I wonder if a better way to achieve it might be to have it behave like the described competitive one but with automatic recommit - individuals commit to certain goals (which don't necessarily have to be the same! e.g. for a work goal if someone works part time they might want to commit to a smaller fraction than a full time coworker. Actually work goals are probably a bad idea because you want a way for people to be personally accountable and taking their personal money is shitty), these are plotted on the same graph, when an individual falls below the line it behaves like a normal derail.
Once I add my goal to a category, there could be a public gallery page of all goals in the same category. Similar to how the beeminder.com/meta gallery brings together some of the goals from the core Beeminder team's individual pages.
The public gallery would need to do something about off-the-road and successful goals, perhaps sweeping them to below the line after a day of shaming (or triumph). Otherwise all of the goals at the top of the page would all be inactive goals. (Plus the reverse of putting unfrozen goals back above the line.)
Viliam Búr commented
Cooperative goal: A group of people commits to do 1000 push-ups in total each day. Everyone enters their own data per day, but they see the contributions of everyone. When the path leaves the yellow road, they all lose. A pie chart shows how much each individual contributed to the goal, and especially who didn't, so the contribution can translate to a group status.
Competitive goal: A group of people commits to the same thing. It is as if everyone would do their own goal, except that all paths are shown in the same graph. If someone's path leaves the yellow road, the given person "dies" (can no longer enter data in this goal), but the remaining people continue. (When specifying the goal, there could be an optional rule that if only one person remains, the goal stops, either immediately or after one additional week, because the "winner" no longer has a motivation to compete.)