the public interest is a is a term which describes "that which is in the interest of the public at large".
That is to say, once the special interests and private interests are all tallied up and balanced against each other what supposedly emerges is what would be the alternative which did the most good for everyone.
The difficulty and subjectivity involved in determining what is in the public interest generally defies it being captured by experts, theories or philsophies.
Using the internet, a wiki can approximate an open market for ideas, which by assimilating a lot of information from a large number of participants, can concievably capture a "snapshot" of what a large number of people find generally agreeable. This has become the centerpiece of a lot of debate reguarding what efficient civics would look like.
lobbyist, grassroots democracy, politics as usual