Rain, as far as I know (and I definitely could be wrong...) there isn't a specific limit on cheese. However, you are supposed to limit your saturated fat intake as much as possible, and since fat free cheese is pretty disgusting, you're going to be getting some saturated fat with each serving. So, yes, you need to limit your intake. By how much? Depends on your cholesterol level, what other kinds of saturated fat you are consuming, etc. If cheese is your only source of saturated fat and you are eating reduced fat or light cheese, you might be able to get away with more than 2 servings a day.
I hope that helps, though I know it's a bit confusing. One of the things I have a love/hate relationship with on SBD is that it gives us the freedom to take responsibility for our own eating and teaches us to pay attention to what our body wants and needs. That means that there aren't as many 'hard and fast' rules as there are on other plans, but it also means, I think, that you are more likely to stick with this plan and make it a major life change/way of life--you learn so much about what your body is craving and what makes you healthy and fit.
Personally, I have cheese every day!