I've been working on MFC since 2009, and I've never not been paid. So no, they aren't a scam.
I have four questions for you.
1. Are you a man?
If you are, that's why you haven't heard back. MFC is very open about the fact that they only accept female models. "No dicks here" is something they say, and advertise. (This is not meant as an insult, or even insinuating that you are. It's just that you don't say, and you haven't really given us any links to your modeling on other sites, and your username doesn't give any clues, so we really have no way of knowing if you're male or female. While MFC only allows women, other sites allow male models, so... yeah...)
If not, read on.
2. Did you submit all the pictures required, and fill out the info properly?
3. Do you live in the Philippians?
MFC had too many issues with models from the Philippians, so they don't allow models from there to sign up.
4. Did you try signing in to the model admin site with the username and password you chose?
http://www.myfreecams.com/model_admin is the link that I use, though there is a different one which also works.
I don't remember actually getting an email from them when I signed up. I remember waiting a week, then trying the username and password which I submitted and lo and behold, I was in! Really unprofessional, yes. But unprofessional does not equal scam. I'm definitely not much of a professional (which is why I don't do appointments, custom requests, or make promises about when I'll be online.), but if you tip me to do something right then (which I agreed to do), I do it, and if you tip me to do something later, I get around to it eventually! I don't lie about what I'm willing to do or not willing to do. I don't lie about how much experience I have. I don't lie about whether or not I enjoyed something. In no way am I scamming people by misrepresenting what they will be purchasing. But, I'm definitely not professional.