I don't see them as at all necessary for self-defense, unless of course you're already staring down the barrel of another gun. And that's more likely to happen if guns are permitted for civilians in the country in the first place.
From Wikipedia (I know, I know, not the most reliable source but we all still use it):
"The United Kingdom (except Northern Ireland) has low levels of gun ownership and generally one of the lowest rates of intentional gun deaths."
From the same page (concerning America):
"About 10,000 murders are committed using firearms annually."
"The American Journal of Public Health conducted a study that concluded "the United States has higher rates of firearm ownership than do other developed nations, and higher rates of homicide. Of the 233,251 people who were homicide victims in the United States between 1988 and 1997, 68% were killed with guns, of which the large majority were handguns." "
(Link: http://en.wikipedia.org/wiki/Gun_politics#United_Kingdom )
From another page I just Googled (dunno how reliable it is I admit):
"Children and Gun Violence
In a single year, 3,012 children and teens were killed by gunfire in the United States, according to the latest national data released in 2002. That is one child every three hours; eight children every day; and more than 50 children every week. And every year, at least 4 to 5 times as many kids and teens suffer from non-fatal firearm injuries. (Children's Defense Fund and National Center for Health Statistics)"
"America and Gun Violence
American children are more at risk from firearms than the children of any other industrialized nation. In one year, firearms killed no children in Japan, 19 in Great Britain, 57 in Germany, 109 in France, 153 in Canada, and 5,285 in the United States. (Centers for Disease Control)"
Now look at school shootings figures at http://en.wikipedia.org/wiki/School_shooting#Notable_school_shootings .
Look at the American list, then look at the European list. Far smaller, and taken from many more countries.
Of course America is bigger and so on and so forth, but the numbers are ridiculous. Politicians blame bloody video games for school shootings, yet plenty of them (mostly Republicans) think the level of gun control is just fine.