Fun example of the bystander effect in everyday life: last night, I hosted a Twelfth Night party, where people came over and all read the the play aloud and ate boozy cake ("Dost thou think because thou art virtuous, there will be no more cakes and ale?")
We all had a lovely time, and someone asked why we hadn't done this before. And I realized that it was because Shakespeare could happen any time, so we were never pushed to schedule it any particular time. We only managed Twelfth Night because it's pegged to the actual holiday of Twelfth Night.
I think this is more about Schelling points than the bystander effect. "Everyone agrees to have Shakespeare parties at time X of the year" is a Nash equilibrium for every X, so in practice the easiest way to decide on an X is if some particular X stands out in some way. This is why Christmas, Thanksgiving, etc. are nice; otherwise an entire family (not to mention their employers!) would have to agree on what time of year is a good time to meet, etc. There may also be a scarcity effect involved in only one X standing out and the feeling that it wo...
If it's worth saying, but not worth its own post, even in Discussion, it goes here.