What use is the PSVI?

I would like to adapt Ron Bourret's question.

In situations where there is controversy I have often found it helpful to go 
back and analyse the basic (and often unexpressed) assumptions that different 
parties are bringing to the table.

So here are some very basic questions:
1. What is the PSVI good for?
2. Who benefits by the existence/imposition of the PSVI?
3. Who is harmed by the existence/imposition of the PSVI?

Andrew Watt