Hashtags are a community generated statement of collaboration.
Thine hashtag is a jealous hashtag. Love and fear thine hashtag in equal measure or He shall bring down the wrath of Goatsee upon thee.
A hashtag is not a slogan, a mission statement or a viral marketing campaign.
Thou shalt not covet thy hastag for thy marketing website, or stale astroturfing shall smite thee and thine children and thine children's children.
Hashtags can neither be created or destroyed. Hashtags emerge from the will of the community.
Ask not what your hashtag can do for you, ask what you can do for your hashtag.
(FWIW, this post was written before the #ukedchat debacle...)