I think it's pretty bad that something run by YCombinator, a company trying to build billion dollar companies, has outages - and where they don't have immediate redundancy.

"do them much harm."

Hard to quantify "harm".

But I will say that anything that is a habit, when broken, opens you up to the possibility of being exposed to a new habit "the addiction".[1]

Along those lines 1 day of downtime probably isn't going to shift attention much. But an extreme, 2 weeks, would certainly break some addictions as people would fork to a new (I don't know insert some french or latin word here!) So who is to say where that slippery slope of is? (Somewhere between 1 minute and 2 weeks).

[1] Reason that I have heard that Starbucks renovates restaurants at greater expense and keeps them open at least some hours. Because people's habits are mercurial.

Yup. This is why practices like fasting, or change in environment / traveling is good to help you get out of routines - to see what you've been conditioned to and what habits you've formed.

Sadly, I agree. But only because there's not a viable alternative. It's like if YouTube goes down for an hour, everyone whines but really nothing changes.

I wouldn't say that. I think they are competitive because they focus on what is important and disregard the rest as much as they can. And high availability is clearly not what is important for success in this case. With Youtube I wouldn't be so sure...