If you want to save yourself some potential embarrassment over the Steam games you drunkenly bought at 3 am during the latest Steam sale you'll be glad to hear that Valve's client will soon let you hide your unwise purchases.
One of the Steam Client Beta features is listed as, "Add 'Hide this game in my library' functionality, accessible from the Set Categories menu. Games that are hidden will not show up in library filters except for a new filter called 'Hidden', which will only appear once at least one game is marked as hidden. Hidden games are still available for play and will still appear on the user's profile. "
A quick look at Reddit shows the latest beta build is proving to be pretty popular. The features tested in the Steam Beta are usually rolled out to everyone before long at which point you can hide Dangerous High School Girls In Trouble and Putt-Putt.
If you've done nothing wrong, you'll have nothing to hide but this is Steam we're talking about.