Possibilities of Fine Grained Access Control?

I need a solution for the following: With all data stored in the same
schema, consumers may only retreive and update data that is relevant to
them. At the same time, users in our own company need to see all data.

Is a solution similar to Oracle's Virtual Private Database possible with
PostgreSQL, as this is precisely what we need?

thanks,
Uden

Documentation:
http://www.oracle.com/technology/pub/articles/10gdba/week14_10gdba.html
http://www.databasesecurity.com/oracle-vpd.htm