Currently in ArcGIS.com, ArcGISExplorer Online users have the option of opening another user's app, copying it (aka saving it under another name to their account), then customizing it by adding new map services, markup, tweaking layer transparency, etc. It'd be helpful if a user could sync, or compare, their customized app against the original app to see if the original author has added/dropped any map layers, changed the URL for a map service, etc.
On a side note, it'd be really interesting if ArcGIS.com could report to an ArcGIS Explorer Online app author how many copies of their app are made over time, giving the author a sense of how heavily their app is used.
