The channels are run by individuals, which introduces moderation issues and squatting problems. (Also, who gets to run which channels, who do they get them from, etc). Doesn't seem appropriate for a decentralized system.

Also lots of segregated content siloing. When there are topical channels, "the global feed" starts to go down in quality/breadth and people start to second-guess "where" they should post certain notes.

I dunno, I think it makes things feel even quieter.