The Steam Summer Sale is over, but Valve is now in the limelight, and not for a good reason. The digital game distributor giant has rolled out a change to its API, which removes the +1 count for games, to which it no longer has rights to.
In case you didn't know, the number of games in a user's Steam library, is used by Steam for the user's level, which in turn has some bonuses, badges, etc.
Now, just because the games are no longer counted towards your total count, doesn't mean you cannot download them anymore. They will still be available in your game library, and you can download and play them anytime you want to. But the store pages of affected games, are no longer available, possibly due to the fact that they are no longer purchasable. This includes some good games such as Driver San Francisco. It appears this change also affects achievements and badges, as in they are no longer available.
Steam should have at least made an announcement that it was going to roll out such a change. Many users have panicked that some games which they paid for are no longer have the +1 count towards their library.
If you want to see the list of affected games, you can view it on Pastebin.