The only genuine downsides, to me, are the limited scope of conversations and the flood of links that I have no interest in following.

If you want to talk about something other than Bitcoin, and now sports :), there's not much interest and it's not clear how to start those conversations.

Over time, I imagine people learn to stop posting content that no one engages with, but as SN grows and new generations of users fish for sats, there are going to be lots of unwanted links.