Steam now lets you mark games as private
If you've opted in to the Steam client beta, you can now mark games in your Steam library as private so that they're invisible to other users. That means that if you're - as a hypothetical - a games journalist who once had to buy and install some games with questionable names and subject matter for an article you were writing, you can now hide that so it's no longer visible to your friends or - hypothetically - your child.
Hypothetically!