JIT compilation doesn't work unless the components are type safe
type system violations can lead to compromise of evidence, policy, and gateway classes, which can allow malware to escalate its own privileges
all components in .NET are required to be type safe

takes a permission set as input and produces evidence as output
takes evidence as input and produces a permission set as output
takes an assembly as input and produces evidence as output

allow the enterprise administrator, machine administrator, logged on user, and the developer of the application in use to restrict what code can do.
are always kept synchronized via Active Directory
are managed via XML configuration files stored in the same directory as machine.config

will always be used no matter where it is in the tree
is only useful if the private key for that strong name is kept secure
will be ignored if strong name validation is disabled
If you hang security policy off a strong name, or even an authenticode signature, the corresponding private key must be kept secure. Otherwise a bad guy who steals the private key can sign assemblies with it, granting him elevated permissions.

machine-wide, by an administrator running CASPOL
process-wide, by fully trusted code setting SecurityManager.SecurityEnabled=false
and this causes all demands to succeed
and the tools don't make it obvious that it's off
all of the above