The ArcGIS 10.1 help on interactive toolbar tools for LAS datasets identifies one such step:
However, the tools are not always active when working with LAS datasets and the 3D Analyst toolbar tools. The 3D Analyst toolbar tools are only available when a LAS dataset is displayed as a full resolution triangulated surface. A full resolution surface is indicated in the table of contents when 100% of points are being used to construct the triangulated surface. When the LAS dataset is displayed as a point set the tools will be disabled.
What does 'full resolution' mean? According to the ArcGIS help on the topic, the definition is, "the scale threshold used to control when the LAS dataset will render itself without thinning, using 100% of the LAS points." So once you have modified the settings or zoomed in far enough to see 100% of the LAS points, you can use all the tools in the 3D Analyst toolbar, right? Almost.
The final step is to choose the Elevation option from the Display As TIN options on the LAS dataset. Once you make that selection, you should see the LAS dataset appear in the drop-down for the 3D Analyst toolbar and the tools should become active.
Now you can create the profile graph or generate a 3d feature just as you would with a normally recognized surface in ArcMap.
Additional information on Lidar and LAS files:
Additional blogs on LAS dataset: