one is squeak-e - capability based security that lots of others are playing with.
The other is something called islands - literally hunks of runtime/data with no references in or out. If you can't reach it you can mess with it.
I'm not particularly well versed on these technologies but they are being addressed.
Finally, you can get "walls" by running things in different VM's as they're just different unix processes.
I'm not saying walls are bad - just that we've put a whole lot of them in stupid places (and not enough in others it seems).
I think this horse is pretty much done.
Fun discussion - thanks.