Private symbols vs property attributes

[Brendan Eich]

Kevin Smith wrote:
> If you added just one symbol to the internal interface of an object, 
> the whitelists at all trusted proxy-creating sites would also have to 
> be updated.

Not arguing with your larger point, but this is why the whitelist is a 
live object, that is, the proxy code consults it by reference instead of 
making a copy. Tom has shown that for membrane use-cases a shared 
mutable WeakSet singleton.

/be