I don't really agree that this is a good way. 90% discount is obviously a mistake and it is more than their right to cancel those orders. I would fully understand that.

Processing those orders doesn't seems that fair to me. Same rare people get 90% (!) off, all others don't. And FCFS isn't a cool, really fair principle. It is often used, because it is easy to implement and doesn't require more information than just time.

Also I expect the rate of people who ordered just because it is cheap and have no real appropriation is pretty high on that discount. Not talking about people who just wanna resell it on eBay.

What else could they have done?

  * Make a general discount (e.g. 10-30%) for all potential 
    shoppers for the next weeks.
  * Spend the lost money for development
  * Hire more people
  * Donate it to charity
  * Make a challenge in any fair way. Again, time and 
    reaction is a pretty unfair criterion.
  * Sponsorship
  * ...

Again, FCFS is some type of fairness, but I think a pretty bad one.

Also not sure if this is real marketing. Are their clients really that community based and speaking about such thing? Aren't more just angry because they hadn't the chance to use the opportunity?

Facebook comment (from source): "Well that's absurdly consumer friendly"

TL;DR: If you give some customers 90% discount for no reason, it means unfair prices for all others. Is that really consumer friendly?