The “Reply All” email option can be a useful tool. But it is also a dangerous foe, as the CEO of one start-up apparently figured out. The main lesson here is: Don’t tell a customer to “f&%$ off” even if you’re a million percent sure he or she won’t see it. Because that Reply All button is a sneaky son-of-a-you-know-what, and you will come off looking like a bad company. [Valleywag]

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