They're worth whatever price shareholders meeting at McDonald's can agree on. Search Craigslist for buyers-sellers. If there are zero buy offers, they are worthless.
'...So what your saying is BioAmber never filed through the courts to cancel the shares to declare them worthless. Guess they ain’t worthless then lol..."
"It is easier to fool someone, than to convince them they have been fooled."
For those that don't get it, it means that people need to be more careful, and do good due diligence...