this is normally not possible.
The only thing other users could share with you would be the URL/address of the graphs in their statistics, like this one for the "test" user (which, of course, is so full that it hardly makes sense any more :):
This graph is updated each time the user has a look at his statistics. E.g. if he never has a look at it, it doesn't update automatically.
A while ago, these image files were just called "kochX.gif" where X was the user ID, but I eventually changed it to improve the user's pravacy, to a hash that's not guessable by the user ID anymore. When one shares this URL, however, others can keep up with their progress.
It'd be worth a thought whether there should be improved facilities of sharing one's results, e.g. in order to enable teachers of CW courses to keep track of their students' progress...