Drafting up a suggestion at sithjawa's suggestion.
Title: Content filter settings by computer
Short Description: The ability to set content filter settings on a by-computer basis for a logged-in user, as well as by account.
Full Description: There are times and places when even people who are ordinarily all right with viewing explicit content with no warning would appreciate a warning. If someone visits LiveJournal from both home and work, they may wish to have different content viewing settings in each of these places. It would be a bother to go into the settings and modify them each time. It would be far better to be able to set a cookie on each computer that you have logged in at and specify an override to the general content viewing settings.
The new content rating system has the potential to be a powerful tool to help people who want to either avoid explicit content or at least have warning of it. People have historically created safe-for-work custom friends groups to view their friends page by, and asked people to use the <lj-cut> to conceal Not Safe For Work material, but those measures could be made less necessary.
Whether the general settings on the journal have been overridden or not could be indicated with a notice on the appropriate settings page, and an option to turn the override on or off, similar to the "BETA BETA BETA" test feature.
Advantages: More control (and LJ users love control)
Fewer people getting in trouble (with work/family/etc) for stuff that showed up on their friendspage in an inappropriate context
Might be useful to people who otherwise would have no use for the content filtering system
Might encourage people to use it appropriately when creating entries, knowing that people are coming to depend on it for work safety as well as SAVE OUR CHILDRENS reasons
Disadvantages: Would have to be set on each individual computer
Would have to be reset if cookies were cleared or expired
Harder to diagnose if something goes wrong
Might interfere with existing logged-out-user age cookies
People who don't like the system still won't use it, causing problems for people who depend on it
Might not be as easy to code as it seems