Hi,
Hashtags are just trends, or groups of Tweets/Posts that are all lumped together due to a trending topic or event.
Lets take a currently trending item
#StupidThingsPeopleDo
So what a business might do is find a way to insert themselves in a funny and witty way.
**Disclaimer the following example may be neither funny nor witty, but it is just an example
A Skate shop might do something like...
The #StupidThingsPeopleDo when skateboarding {link to video hosted on your site of skateboarding accidents]
That was probably a pretty weak example, but it is the way businesses can capitalize on trends, but only if done in a genuine way and not just throwing in a a semi relevant trending hashtag.
A good way to look at it is possibly categories of a blog, the hashtag is the category tag, but it references the entire twtterverse, instead of just referencing your blog.
In your exact example of Vintage, I would suggest the including of the hashtag vintage when it makes since
Sale today on 70's #vintage clothing click for details (link)
This also is kind of a weak example, but it is Friday, and out of Ideas....
Hope this helps a little
w00t!