Not sure if anyone else noticed this, but the ESRI RSS feed had an interesting item last night.
In preparation for the ArcGIS Explorer community portal, we would like you to test www.arcgisexplorer.com by clicking on the link. If it doesn’t work from behind your organization’s firewall, please e-mail email@example.com with ‘Test Failed’ in the subject. Thank you for your help.
Doesn’t work for me, but it might signify that ArcGIS Explorer is about ready to go public beta. Then again it could be a mistake.