A possibly related item to consider is what options and instructions were included in your request for services. One reason that SEO firms find the doorway scheme attractive is that many clients have told them "bring me lots of traffic, but don't touch my site". In current environment that request is a contradiction. If you want results, the best way is to let them get elbows deep into your site. That other methods (cloaking, etc) may work is true, but also carry some risk. As always, it is helpful to remember that realistic expectations and clarity of task are good ways to start any project.