I'm happy to announce that with our next service pack you will be able to bind RadGridView completely codeless to DomainDataSource in Silverlight 3:
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition Height="30" />
</Grid.RowDefinitions>
<riaControls:DomainDataSource x:Name="DomainDataSource1" AutoLoad="True" LoadMethodName="LoadCustomers">
<riaControls:DomainDataSource.DomainContext>
<localWeb:NorthwindDomainContext />
</riaControls:DomainDataSource.DomainContext>
</riaControls:DomainDataSource>
<telerik:RadGridView x:Name="RadGridView1" ItemsSource="{Binding Data, ElementName=DomainDataSource1}" />
<df:DataPager x:Name="DataPager1" Grid.Row="1" PageSize="10" Source="{Binding Data, ElementName=DomainDataSource1}" />
</Grid> All operations like paging, sorting and grouping are applied to the REST query with minimal JSON response:

Enjoy!