I've tried it with an empty beer can. It wobbled a bit, but it stayed. Then moved on to a half pint glass, wobbled a lot, but it stayed.
Boyfriend has stated that he wouldn't trust me with his beer on my head, as I'm incredibly clumsy and would probably drink it myself. He does however say that I'm a good chin rest when tired or drunk.
How about computer components? Less chance of them over heating!