What some people are doing is creating two sets of circles: circles that categorize people for outbound messages and circles that categorize them for inbound messages. When you separate this, you can now effective keep a short list for when you're busy in addition to following everybody else.

The amount of pain involved in effectively tracking all your friends twice is leading many to suggest that you want some sort of set arithmetic so you can say "this set equals everybody minus these losers" or equivalent. Presumably Google is working on such a thing, but the question is whether such a thing would be in any way usable.