If a social media site can have no downtime Im sure a private health care site that stores very important data wont too if the deploy it correctly with multiple back up servers ready. It is cheaper and more efficient.
Everyone should stop listening to the people like Tim Swanson or Don Tapscott if they say the blockchain will be a part of everything. They are only trying to create a buzz. Listen to the real people who know better.
I've seen twitter and facebook be down before. If the blockchain has been down over the past 7 years, I don't remember it.
Twitter appears extremely broken at the moment with their last update.
Big social media sites usually have incentivized bug programs where exploits in their social media service can be paid in thousands of dollars of cash.
That could cut down on their sites being compromised, which could cut their downtime.
I don't know if that's something all social media providers can afford.
It is possible smaller organizations who can't afford bug bounty programs, might opt for blockchain technology to cut downtime associated with data compromise.
I honestly don't know if blockchain technology is overrated in terms of applications. I guess we'll find out in the next 5-10 years how useful it can be.