First off, I DON'T encourage anybody to filming. Still you could go for something bootleggers call "stealth taping". This means, you won't hold your cam up high to get a perfect shot, but just remain still and silent in your position, trying to film what you can film, including obstructions from people standing infront off you or walking by.
What can happen if you really do this? Well, if you're caught, they might take your cam away or even throw you out. This is not a joke. It happened to tapers before.
So once again, I AM NOT encouraging anybody to tape. Just think about the risks.
Still, if you manage to get through with it, you'll have an audience shot version (complete or incomplete) which might be worth something if you are into bootleg trading or just a die-hard fan.