"[It] may be possible for employers to enforce non-competition forfeiture provisions by including them in deferred compensation top hat plans subject to [ERISA].... This may represent a paradigm shift for employers operating in California; the potential loss of deferred compensation by key employees might meaningfully deter employees from competing, or at least make the choice to compete more difficult. On the other hand, a forfeiture provision may not be enough to change employee behavior or assure the safety of trade secrets and other confidential information."