"Madison" is a surname. The going rage these days is to give your child a well-known surname as her/his given name!
Examples: Taylor (for both boys AND girls), Archer, Tanner, Harper, Madison, Reese (as in Witherspoon), McCauley (as in Culkin), and there are a host of others...really, just pick ANY well-known English culture surname that ends in "er" or "or" and you've got a trendy first name for your offspring, who may yet become a big star and get persecuted by People Magazine and News Of The World! Yeah.
The above is a much more prevalent form of nominal abuse of children these days than naming your kid "Kal-el" or "Chastity" or "Moon Unit" or other off-the-wall things like that.
The things people do to be "different" (ha! ha!). Notice how so many people try to be different in the same way at the same time? Hmmmm...ummmm...gosh! They all look and sound so much the same...
Then there's Kyle. The Scottish name that recently returned from virtual historical oblivion and took over the World! Now someone on a tour boat yells, "Kyle! Get over here right now!" 312 boys named Kyle rush to the port side, and the boat tips over. Another avoidable tragedy caused by trends!!!
Why? Why Kyle? (I heard it was because of some soap opera.)