To reproduce:

public Form1()
{
    InitializeComponent();

    this.radPanorama1.RowsCount = 5;
    this.radPanorama1.ColumnsCount = 1;
    this.radSpinEditor1.DataBindings.Add("Value", this.radPanorama1, "RowsCount", true, DataSourceUpdateMode.OnPropertyChanged);

    for (int i = 0; i < 5; i++)
	{
        RadTileElement tile = new RadTileElement();
        tile.Text = "Tile" + (i );
        tile.Row = i ;
        this.radPanorama1.Items.Add(tile);
	}        
}


Please refer to the sample video: http://screencast.com/t/lncUvh0vIRKN 

Workaround:

 private void radPanorama1_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName=="RowsCount")
            {
                this.radPanorama1.PanoramaElement.InvalidateMeasure(true);
            }
        }