That the thing I miss the most from Facebook. I mean, it still exists, but back then, almost everybody used Facebook, and for actual two-way communication, not for following "influencers" or trying to be one. And that was the true value, the features are nothing special, but the networking effect was unmatched.

It means you could make your invitation on Facebook and everyone was on it, with maybe a few exceptions that could be dealt with separately.

Serendipity is nice, but if you are the host, you need to at least get an idea of how many people will be there. And while we may all be friends, things can get tricky when you start inviting friends of friends.