If you want to give someone else access to your Mac, like a house guest or someone visiting you at work, use the Guest Account instead of letting them handle your real user account. Guest Accounts are easy to switch to, and protect all of your documents, settings and other data from mistakes the guys might make. When the guys is done, the Guest Account is wiped out completely, leaving nothing behind. You should have your own account, and anyone else who 'owns' the Mac with you, like a spouse or other family member should have their own account as well. Anyone else should use a Guest Account.