Quizzle is not a scam, but they do not give you your real credit score - they give you a "FAKO" score which is an estimate of your real Experian credit score. I've found that FAKO scores can be fairly accurate and give you a general idea of where your credit score stands, however I HIGHLY recommend checking your actual FICO scores at least once a year. In some situations FAKO scores can vary from your real score by a hundred points or more - which is huge!
Agreed, Quizzle is definitely not a scam. The best part about Quizzle is they actually deliver every consumer a free credit report and score without asking for credit card info or your social security number; no one else does this. Many advertise the free credit score, but none provide you with the only thing you actually need to understand your credit and work to improve your score. Without an actual credit report, you can't truly understand your credit, analyze to find ways to improve your score, or keep tabs on wrong information, strange activity or identity theft attempts.
In the interest of full disclosure, I am the editor of the Quizzle Wire, a personal finance blog supported by Quizzle. But, I would put Quizzle's tools and customer service up against any other company in the free credit score space. And don't just take my word for it, try it... your credit score and report are totally free.