> > why run 2 unix tasks while you can run one unix and needed amount of
> > processes under it
> 
> Uh, because you have multiple customers who want shell accounts but you
> don't want them to see each other? Because you are hosting web sites

that's why i'm talking about ps ax showing other's processes.
i have about 200 shell and non-shell accounts (in fact all are shell, but
not all owners use it) on linux and people see each other only in
finger but not what they're doing

> for multiple customers and want to be 100% sure a security breach
> in one site doesn't affect a different customer?

what customer-related security you are talking about?
if about insecure customer's CGI - i use suexec so only this customer will
have problems in case of exploiting this. process and memory limits per
shell account is enough to one user not be able to kill the machine.