"SPW 2010 does not support all SharePoint sites. And not all content types of SharePoint lists and libraries as shown below are supported in SPW 2010 either. Calendar, survey, and Wiki are, for example, non-supported types. A SharePoint site with a content type not supported by SPW 2010 will not have the option to “Sync to SharePoint Workspace” in SharePoint Site Actions"
http://edge.technet.com/Media/SharePoint-Workspace-SPW-2010-Explained-Part-2-of-2/