On this link - http://demos.telerik.com/silverlight/#ChartView/Gallery/Linear - I'm trying to find where you set the point label visibility. ShowLables in the code behind is not bound to anything in the xaml... how exactly is it working? magic :) ?
It does look like magic! There is more than you can see directly in the example windows, the demos are there to briefly overview the controls. I can show you where to get the source code for the examples.
If you've downloaded the trial or have purchased the controls you already have the source on your pc. You can find it here C:\Program Files (x86)\Telerik\RadControls for Silverlight Q2 2012\Demos. To get to the example's code, open the solution named ExamplesCS_SL.sln. Then open the project named ChartView, then open the folder named Gallery and lastly the folder named Linear.
Now open the file Example.xaml. Thats the demo you referred to, everything you want to know is in there. The example uses it's own ViewModel inside the same folder, it the file named ExampleViewModel. Inside there you'll find the two items responsible for the visibility of the labels and the checkbox for the labels...