This metaphor has worked well for me too, to show people that they already expect there to be limits on what the government can do to keep people safe--even though they might have not have realized it.

So it's good as a throwaway metaphor for illustrating that concept, but it's not great for arguing against surveillance, because Internet traffic is not the same thing as getting dressed every morning. Most people get a lot less worked up about email and web surfing than being naked.