I highly recommend Bruce Schneier’s blog. Security involves thinking about what how things can go wrong, and that’s an excellent skill for any designer to have. Psychologically people are biased to remember catastrophically bad experiences, and can develop an adversarial relationship to something from just one bad experience, if it’s unpleasant enough. Minimizing unpleasantness can be more important then optimizing goodness, when trying to cultivate a good relationship with users.