I'm not sure that hashtags in your hubs would do anything for you. Hashtags on social media are used to show trends and also for search. I would write your hub and then promote it using the hashtag on Twitter. If your hub was about frugal living or something you could then tweet it out with #frugal #FrugalLiving etc.
Hopefully someone who is more of an expert than I in social media will let you know for sure, but I see no point in putting this in hubs you write. If you keep a blog, you can use "tags" and that's a little different, but served the same purpose. We used to have them on HP and they were taken away.