Have you ever told someone a secret, and the next thing you know it's common knowlege amongst your friends and family??? Well, that's kind of what a Last Will and Testmant is like. If you put personal information or wishes into this document and it is filed with the probate court, well...anyone can't see who you left money to, who you didn't leave money to and why.
Why is this important? Well maybe you don't want everyone to know what you did with your stuff. This can be avoided if you do a Trust Agreement. Trust's are not public and will not be recorded with the probate court. THerefore, you can put as much personal information about yourself, your beneficiaries, etc. and not worry that everyone and their brother will see it.
Read the following article from Forbes, to find out about one famous individual who did just this and now the whole world knows what he did with his $50 million.