Middle names are important to genealogists, but often more important to the individuals who wear them. Just ask John Aristotle Phillips, who runs an identity- and age-verification service.
"Why do I use my full name?" he repeats after I obligingly ask the obvious question. "Do you know how many John Phillipses exist in the US? I do. There are 3,621. There are 853 born between 1950 and 1960 and 282 born in August. There's only one John Phillips born on August 23, 1955. There's only one John Aristotle Phillips." [Link]