For writes, users manually choose. I think this is going to be more and more necessary as relays start requiring subscriptions.

I think posting normal messages, just a few relays.  For posting your relay list, might be smart to post it to many relays so more people can find you.  I'll be adding something for that. 

 There has been some chatter about services that specialize in bootstrapping like this, DHTs, nprofile servers, etc.  I'm staying out of the server-side of things, but happy to subscribe to such things when they exist. 

 What is nprofile server? A relay that basically collects all kind:0 events from other relays? 

 I was just mentioning something someone else was talking about. I also don't know anything about DHTs. These are just words I hear bandied about when talking about services that help people find people.