There are too many people named Colin in the US these days. When I was a child, Colin was an unusual name here. I was teased. Kids called me a girl, saying my name was "Colleen." They had never heard the name Colin.
In my birth year of 1960, only 7% of names given to boys in the US were more uncommon, according to a Facebook application that rates your parents on the originality of the name they gave you; mine got an A+. Getting teased was the downside--and there was never a "Colin" on the racks of those little license plates for bicycles with first names on them. The upside was that when I heard or saw the name Colin, it almost always belonged to me. Now, men and boys named Colin pop up all over the place--which can be confusing.