One of the challenges of using federated identities for research collaborations is the need to support many identity providers (IdPs), as collaborations can span many organizations (universities, labs, etc.). As of June 2012, CILogon supports 57 out of 239 InCommon identity providers, plus 3 OpenID providers (Google, PayPal, and Verisign). CILogon is participating in InCommon's new Research and Scholarship program that helps services like CILogon work with large numbers of IdPs. In case a researcher's home organization doesn't yet have an InCommon IdP that works with CILogon, researchers can use an OpenID account (from Google, PayPal, or Verisign), a free ProtectNetwork account, or an existing account with a research community IdP like LTERN.
The chart below shows the percentage of CILogon users from the different IdPs. We see that Google (used by 36% of CILogon users) is currently the most popular IdP. ProtectNetwork (used by 7% of CILogon users) is also popular, likely because ProtectNetwork serves as a "catch all" InCommon IdP and supports ECP for authentication outside the web browser. Then we see a long tail of usage of other IdPs, which is not surprising as researchers come from many universities and labs. It will be interesting to see how the chart changes as use of CILogon grows.