This may or may not be the appropriate place to ask for this but I have noticed that there's no way to "leave" a campaign, other than having the GM take you out of it. In some cases (such as the GM no longer being around) that' is not possible.
Those campaigns then sit, taking up space on your profile, and there's no way to remove them.
I don't know about other end users opinions, but I feel it would be a useful ability to be able to "opt out" of them, so they are removed from your profile.
Never Mind - I found it (Click on Edit Profile, then all the Campaigns have a "Leave Campaign" option)