The DataContext is not distribute to Large and Small contents in some cases.

Possible workarouns:
1) Declare the DataContext of TileView in xaml, for example:
   <Window.DataContext>
        <local:MainViewModel />
    </Window.DataContext>

2) Assing DataContext Binding to the three contents:
  <telerik:RadFluidContentControl.LargeContent>
                <Grid DataContext="

 <telerik:RadFluidContentControl.Content>
                <TextBox FontSize="16" DataContext="{Binding}"

            <telerik:RadFluidContentControl.SmallContent>
				<TextBlock FontSize="12" DataContext="{Binding}"

In Expression Dark theme when you have a TextBlock inside a FluidContentControl the foreground is not updated.

When you have nested TileViews the exception is thrown in certain scenarios

Fixed in LIB version: 2014.2.0825

When the TileView is populated with a single tile and HorizontalAlignment of the control is set to Left, and then maximize this tile, the tile disappears.

Fixed in LIB version: 2014.2.1005

If all RadTileViewItems have their Visibility set  to Collapsed and MinimizedRowHeight or MinimizedColumnWidth properties of the RadTileView are changed, the items cannot be visualized again.