"The political argument for PPPs is that they stretch scarce government resources and ensure that they leverage other contributions of money, expertise and other in-kind resources. The initial emphasis on PPPs came from the Reinventing Government initiative under the Clinton administration, but the George W. Bush administration was also enthusiastic."
A really nice piece (Zakaria's blog is always fantastic place to find intersting takes on what's going on in the world), but I think that it completely ignored the biggest reason why this evolution is occuring: Social Media.
I think that public-private partnerships are going to continue to grow in importantce when it comes to the "heavy lifting" of foreign policy (i.e. nuclear proliferation, etc.), but this is coming out of a reality that has existed for several years but has only recently snuck up on the career politicans and the diplomatic corps: Governments already matter less when it comes to foreign relations.
Sites like Facebook and Twitter allow people to maintain relationships regardless of geographical or political borders. Other sites, such as Couchsurfing, encourage and facilitate real-world interaction and relationships, which Facebook and Twitter then help to maintain/deepen. The role of government in defining or shaping a person's iteraction with a country (or its people/culture/economy) is shrinking. Fast.
For instance, China's relationship with the US has little real effect on me here in Beijing. I don't interact with the government nearly as much I interact with people. Whether or not Obama moves troops to Australia or if Vietnam invites US naval vesels into their sections of the South China Sea has very little influence over mine and my friends' relationships. Whether Putin and Medvedev actually hold fair elections in the coming months doesn't effect my relationship with my girlfriend or our good friends in Moscow.
Sure, there are measures that countries can take to cut off peoples' access to one another or to social media and money, but these are extreme cases and outliers (North Korea, Iran). Travel has never been more accessible and the flow of information and capital has never been so proliferate.
In the near future you'll see governments sliding towards placing a greater emphasis on two items in their foreign policy stances: 1) The tracking of interactions between their citizens and another country's (not necessarily in a nefarious way, but in a similar way that they currently track financial transactions - see this fabulous map for an example of how this could work) and 2) a focus on interacting with another country's people directly. Even today the US is having more of an influence in Iran and Syria than it has had in decades by dealing with the PEOPLE there instead of the strongmen.
In the near future foreign policy will be directed more by people's interactions than the policies of governments.