Jason Corsello has a post about platforms with a HCM lens (based on a post from Marc Andreessen about three levels of internet platforms). Jason points out that HCM applications are at the first platform level (Access APIs). I think there is a simple answer to this though. HCM application providers have not tried to be platform providers. We may see that happen down the road. However, I think what will be more interesting in the short-term is how new and existing vendors leverage level 2 (Plug-In APIs) and level 3 (Apps Run Inside the Platform Itself). I imagine that we will see numerous Facebook plug-ins emerge (Jobster for example has already created one). I expect that we will also see someone build serious HCM applications on the Salesforce.com Force.com (used to be Apex and before that AppExchange) platform. CODA, a financial software vendor, announced this week that it is building financial apps on the platform (see Dennis Howlett's post on this). It is only a matter if time for HCM for the reasons Andreessen outlines about level 3 platforms.