It's an interesting experiment, but I wouldn't call it a "social" network. 1 message a minute wouldn't allow you to build communities or have any reasonable discussions.
Incorrect. Fidonet and Usenet are two examples of built communities that were able to have reasonable discussions with up to days or weeks between messages.
Regardless, since both thrived at 1 message per minute or slower for years, your blanket rejection of non-realtime social opportunities is shown false.
I'm curious what that does to discourse too. If there's no advertising allowed and users bid on one post per minute, what's to stop someone with deep pockets from dominating the system?
I do think bidding to post and rate-limiting is an interesting solution but it seems like there needs to be some kind of scaling mechanism.