As soon as I can after a shoot, I download my cards and back up the images into at least two places. Why? I am paranoid.
When I travel, I download and email or upload the best images to an online service, just in case something goes wrong. I teach my students this same thing.
A New York City photographer may want to evaluate his backup system – keeping the original cards and the hard drive used to back them up together can cause you some severe problems.