supporting muscle groups never get the true stimulus they ned to really grow.
Once again, the "stabilizer" argument for freeweights is incorrect. The reason is that no muscle acts solely as a stabilizer. The term itself is contextual, in that some movements use a certain muscle to stabilize, when different movements use the muscle as a prime mover. There are also a few different types of stabilization.
So you won't be lacking "stabilizer" development if you only do machines, assuming that all muscles see work as a prime mover at some point in your routine. Yeah your abs stabilize a freeweight squat and don't stabilize a leg press, but if you go on to do weighted crunches the following day, the difference is rendered moot.
I would use machines a lot more than I currently do. I do mostly freeweight exercises not out of a belief that they will make me bigger, but because I switch gyms a lot between college and home. It's vastly more convenient to know that everywhere I go, there are dumbbells and olympic barbells and I won't have to retest all my maxes.
There are actually certain movements for which a machine does a much better job than freeweights. A few that come to mind are pullovers, lateral raises, and ab curl. These are exercises whose freeweight motions produce a greatly variable tension on the target muscle. The use of a machine with a CAM system can even out that resistance.
That being said, I think n00bs should be put on freeweight stuff to develop balance, core stabilization, and coordination.

Endpoint brought up great points.
-casualbb