New Post: Must clone each feature to create new layer?

Hi!
I had the problem that a new feature layer that I created could not be added as a layer to the map control. MapControl.Layers.Add(newFeatureSet) returned an exception that informed me that the index key had already been added. The problem was that when newFeatureSet was populated with features from another feature set as references instead of cloning each feature.
Is this as designed?