No, of course Square is harder to fail-over than YouTube. There's no such thing as a lost monetary transaction on YouTube (a lost ad click at most).

From financial liability point of view, and also from PR point of view, it may be better to completely shut down and not accept payments than to take money from a buyer and fail to transfer it to the seller, or bill somebody twice, etc. Eventual consistency is OK, but final consistency should be guaranteed.

Because of that, it's harder to run stuff like chaos monkeys, DiRT-style exercises, etc, in an institution that handles relatively large and well-tracked transactions. Hence it's harder to stay prepared to various disaster scenarios.