I agree it's fun. I'm on it all day whether at work or at home. It's an awesome, awesome tool...
But at it's core it was created and meant to be a user-driven product.
If companies and organizations tell people "Hey, here's the hashtag for this event, use this" it lessens the impact individuals have and puts all the power into companies. It's great to have a hashtag for an event, but many times a few users will create one and people will build off that, that's when it works best. #FirstWorldProblems wasn't created by a company, it was groups of people using it and eventually it blossomed into something with millions of Tweets a day. That's the beauty of a user-driven product like Twitter.
I understand why a company or a football team would try and get people to use a particular hashtag or why some companies sponsor and pay a lot of money to promote their hashtags, I've done it at the university plenty of times.
I just think having it so much out in the open and forced will over time cause overexposure and must like Facebook or MySpace people will begin backing off because they feel it's so initiated with companies/organizations driving the car as opposed to users.