Setting aside the act of mass datacide that moved Google up my corporate evil scale, G+ suffers from a fundamental Circle problem. It may be an attempt to work around Facebook patents rather than a misguided design, but either way it doesn't work.
G+ provides these tools for publication and subscription:
- A single identity. (In this case, identity is equivalent to a maximal set of Identity-Circles + Public)
- Circle: both Access Control and Topic definition and Subscription-filter option
- Person level blocks
These aren't sufficient. They put far too much of a burden on the publisher to create and maintain a multitude of Circles that pre-coordinate Access Control and Topic definition . The pre-coordination work fails due to combinatorial explosion .
A full set of controls looks like this.
- Multiple identity: where identity is a set of access controls and topic definitions.
- Access controls: who can see what.
- Topic definitions: what are the topics, so subscribers who can see a stream can choose what they follow within that stream
- Person blocks: hide all comments from a person
A full set of controls seems more complex, but the workload largely falls on the Publisher, not the consumer -- and the combinatorial explosion problem is resolved. Subscribers choose which topic to follow. Unfollowing all topics is equivalent to blocking a person's posts but not their comments.
Google Reader Social had no access controls (that I remember), but it did allow multiple identities (an identity is equivalent to a subset of topics). The topic controls were very weak (subscribe to tags - almost never used), but the UI made it very easy to pick items of interest from a large stream. The G+ UI makes the combinatorial problem much more significant.
Google has promised pseudonym support. That will be roughly equivalent to a subset operation on Circles. Boolean operations on Circles would also somewhat alleviate the publisher combinatorial problem.
Alleviate, but not eliminate. Sooner or later, G+ will need to separate access control from topic definition.
(I'm grateful to a G+ comment from Peter C that helped me think this through.)
 Note too the 3 people on earth who'd probably appreciate this. This is identical to the pre- and post-coordination problems that bedevil anyone who works with concept based knowledge representation ontologies, including clinical terminologies/vocabularies like SNOMED and (yech) ICD-10-CM and ICD-10-PCS.
 A Sept 2011 WSJ post on "injury by falling turtle" in ICD-10-CM causes of injury illustrates this also. See #1.