I’ve heard before: What’s the harm? Why not at least try to include #SuperBowl if every little bit helps? Somewhat of a fair point. Using a hashtag does no harm in the same way wood paneling does no harm to your station wagon, or a misspelled tattoo does no harm to your bicep.
Here’s where I’ll join the rest in unquantifiable hoodoo: I believe hashtags are aesthetically damaging. I believe a tweet free of hashtags is more pleasing to the eye, more easily consumed, and thus more likely to be retweeted (which is a proven way of growing your audience).