According to the documentation, ArcFollowCamera (and FollowCamera, maybe others too?) setTarget() method should be able to accept either a vector or a mesh, but it only accepts a vector. Therefore the only way I see to set mesh as target is to do it in the constructor. The ArcRotateCamera setTarget() does accept either a mesh or a vector.
(BTW, BabylonJS rocks!)
Thanks!
Here is the small example with switching camera targets - Babylon.js Playground
As it is written in Documentation, setTarget method accepts Vector3 parameters.
To set mesh as a target you may use mesh.position
It does feel, however, that the Follow cameras should have a setTargetMesh function.
I also believe he refers to the documentation mistake of the TargetCamera’s setTarget function that states “mesh or vector”, but accepts only Vector3. In this case - it is a documentation mistake. We accepts PRs to solve this 