Hashtags are kinda silly and overly promoted in social media, but they can be useful for some things. For example, you can use them in chat conversations to find information or links you'll need later.
If you're like me, you have lots of movie recommendations, YouTube links and to-do reminders sitting in your chat history. When you're having a conversation about something you'll need to come back to, MakeUseOf suggests including a hashtag so you can easily search for it and similar suggestions later.
Of course, you'll probably only want to do this with close friends or coworkers who won't judge you for using hashtags in chat conversations.