"For those powers that can actually pose a threat to others (e.g., explosive energy blasts), there's a point here..."
Good. Now we're getting somewhere, Vitruvian. There's a case to be made, for taking special precautions for low-probability, high-impact events, when they've suddenly become a bit more likely.
It doesn't necessarily mean that all such individuals have to monitored or have their identities revealed to power structures, who themselves haven't fully justified their own existence. But it does mean, that in THAT case there's room for debate, for a funneling of tax revenue to help lessen the impact of Black Swan events. And a discussion - not a threat - with such individuals is justified.
When it comes to other types of superpowers, like perceptual enhancements which might be useful for activities like whistle blowing, then it would be an absolute mistake to trust the authorities to deal with such individuals wisely. Nevertheless, I wouldn't blame them for trying to do so; in their position, they would feel like they had no choice.