I have always viewed hashtags as open and not able to be owned by anyone. We have seen this effect a few times when corporations use them and then society responds with their own version. A great example is what the NYPD tried to do and how it backfired. What your saying sounds a lot like how the DNS system is currently setup and I am not a fan. Currently in a udrp case for my company because of someone cyber squatting a branded URL of ours.