I use them as a way to search generically for a specific topic without knowing the exact text.

Say for instance I write a helpful guide as a reply to someone on a specific topic, and tag it with a hashtag. Assuming other use like-kind hashtags you could easily search for something like #coldstorage and pull down all the posts with that tag. So essentially the same function as Twitter (at least how I used them). Perhaps what you have implemented would work the same way.