What's the deal with the whole # thing on twitter?

[Sarah]

It's called a hashtag. Most times they just refer to a certain topic, which makes searching for posts about that topic easier. Other times, people use hashtags to make short passive-aggressive or sarcastic remarks, such as:

Ugh, my iPhone is so slow today! #firstworldproblems

In that case the hashtag indicates that they aren't seriously annoyed about it, they're either being sarcastic/making fun of people who are seriously annoyed about having slow iPhones, or saying that they know it's a little thing, but they're going to be annoyed about it anyway.