It's not uncommon at all in the technology industry for workers and executives to move from one firm within the industry to another that is a direct competitor. Typically we see this when companies start looking for engineers and other folks to help it better compete in the market. On occasion, we see executives leave and head to a competitor of their former employer.
KitGuru reports that NVIDIA VP Manju Hedge, VP of CUDA and PhysX has left NVIDIA and headed to AMD. AMD directly competes with NVIDIA in key categories like GPUs. KitGuru doesn’t expect the departure of Hedge to spell any disaster for NVIDIA.
It's also unlikely that AMD will glean and NVIDIA secrets from its new employee considering the mass of NDAs Hedge is certainly under. Perhaps Hedge will be able to help AMD sway game developers to support some of its ideas like HDR with AA. Hedge was key in gain support for CUDA at NVIDIA.