I think that people should be careful about giving out their personal information because people can steal your identity.  There are many ways to keep from bieng robbed in such a manner.  One way is to do not give out any information about your social security.  Another way is to not give out your phone number.  Finally, you should never use your last name.
First if you give out any information on social security then you are an easy target for thieves.  If you give out your phone number then people could call and persuade you to give out private information.  Finally, if you use your last name then people could harasses you by phone from looking up your last name.