Walter,
Assumes you connect to a remote database through ODBC or OLE DB which will load data into ADO.NET ADO.NET datasets/datatables don't necessarily assume a remote database for loading. You could have electronic scanning that dumps out XML data to be read into a dataset. (yes, the back-end DB is the most common way to describe ADO.NET, but it doesn't assume a connection. You can create ado.net datasets that never have anything to do with the back-end dB).
Yes, you can pass datasets around as they are objects. You can now also serialize them in a binary format when passing across application boundaries (provided both sides are running .NET apps).
Kevin