If you need, besides major accounts, an extra account with limited access to data, you can add Windows 8 Guest account. The process is almost the same as in Windows 7.
If you know how to sing or hum a song, but don't know the title or the artist performing it, you can use a midomi website which will help you find the the song.
If you are a "private" person and don't want your profile picture or name to appear on your friend's feed next to ads you liked, then follow this steps.