Even the government thinks it's a good idea!
A while back I wrote a blog regarding why a person would want to own an AR-15 rifle. Since I've written it, it's been one of my most read posts. If you don't want to read it, the first reason is it's the best tool to protect your family currently available to civilians. It seems the Department of Homeland Security agrees with me!
They recently put out a request for bid for defense rifles for personal use by their agents. The document describes characteristics and requirements for 7,000 rifles. Of course, since they are government workers, they rifles are called out to have "selective fire", meaning they can be fired full-auto, what a layman refers to as a machine gun.
So basically, Homeland Security wants to buy a bunch of M-16 rifles for their employees to use for protection, similar to the AR-15 you may want to use for home protection. Keep in mind, this isn't a military purchase, this is for bureaucrats. People with office jobs just like what you may have. I think that calls out what I've been saying, the AR-15 platform is ideal for personal defensive use, even if you can't get one with "selective fire" capabilities.
If you read through the documents, you'll notice that this type of rifle is being sought for it's suitability for personal defense. Specifically sought for it's suitability. Meanwhile, other government bureaucrats are promoting legislation to strip citizens of that very rifle. This is somewhat bothersome. I don't think just because your job is for a government agency rather than a manufacturing company or a bank or a farm you should be awarded special privileges. The people in power must disagree with that idea, however.
If you want to see someone break down this topic in more detail, you can do so here.