Question: why would my mother ask me for my social i.d. number so she can put me in her will? 

Answer: I'm an attorney, so I'll try to give you an intelligent answer, unlike some of these others. From what you've stated it seems that your being placed into her will as a beneficiary, or other things. \n\nIts mainly used to help identify people after your mother has passed away. If its bothering you go speak to her about it.
This example question from the Yahoo Q&A forum is categorized in the topic: Society & Culture