Lindsay Zoladz, in Pitchfork, looks at the hashtag as a powerful linguistic shortcut and its "culture-jamming" possibilities:

If you have any doubt that the hashtag is a frighteningly powerful tool in our modern vocabulary, imagine a person you care about texting you that song's title line out of the blue: "You're beautiful." Now think of the same person texting, "You're #beautiful." The second one is jokey, ironic, distant—and hey, maybe that's what that person was going for. But it also hammers home that point that the internet too often asserts: You're not as original as you once thought. "Beautiful" is analog, unquantifiable, one-in-a-million. #Beautiful, on the other hand, is crowded terrain. Ten more people have just tweeted about something or someone #beautiful since you started reading this sentence.

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As more and more of our daily interactions become text-based—people preferring texting to phone calls, workplaces that rely heavily email and instant messaging—we're developing ways to stretch our written language so it can communicate more nuance, so we can tell people what we mean without accidentally leading them on or pissing them off. Periods have becomemore forceful, commas less essential, and over the last few years, the hashtag has morphed into something resembling the fabled sarcasm font—the official keystroke of irony. Putting a hashtag in front of something you text, email, or IM to someone is a sly way of saying "I'm joking," or maybe more accurately, "I mean this and I don't at the same time."