Collaboration Ecosystem substantially expanded the use of Public Key Infrastructure (PKI) by allowing user communities to operate their own Certificate Authorities (CAs).
Certificates for anything can now be generated easily and independently as needed.
The distributed nature of Community CAs complement existing centralised Public CAs, enabling end users to control the identity and security of their information environment in details never possible before.
For details on how the ecosystem PKI works in real life:
http://oztell.org/public-key-infrastructure/