What are some of the drawbacks of comparing a company's financial ratios to those of other companies

Question:

What are some of the drawbacks of comparing a company's to those of other companies within the same industry?
Financial Ratios
The term is enough to curl one's hair, conjuring up those complex problems we encountered in high school math that left many of us babbling and frustrated. But when it comes to investing, that need not be the case. In fact, there are ratios that,...