One distinct possibility is that whoever put those slides together made misrepresentations in the case of some or all companies. To me PRISM sounds like it's t

One distinct possibility is that whoever put those slides together made misrepresentations in the case of some or all companies. To me PRISM sounds like it's the front end that analysts use, something that unifies all the different data sources from companies, which in turn vary in their degree of cooperation with the government. The data from Google could very well be the data from specific court orders that name individuals. The join dates could just be the dates that whoever was writing the PRISM software was able to integrate the data from whichever company.