Megan McCardle over at The Atlantic asks the question in light of the impending Heller decision:

So if Heller, as libertarians devoutly hope, legalizes gun ownership in DC, the question immediately arises for those of us who live here: buy one, or not? On the one hand, they are expensive, and shooting ranges far away. On the other hand, I live alone in an apartment that is something less than amply fortified. On the third hand, I'm pretty sure I shouldn't handle a gun when I'm sleepy.

However, I probably will anyway, just because I can.

There is also a "fourth" hand - such that while the decision to keep a gun at home for self-defense is up to the individual, s/he should know the risks involved in order to make the best, and safest, decision. (Currently, by the way, certain long guns can be kept at home in the District. It may surprise some that as of February of this year, 66,019 firearms were legally registered in DC.)