False patent marking occurs when someone marks an unpatented article as patented, intending to deceive the public, and it results in "competitive injury." Though undefined in the false marking statute, competitive injury can be loosely defined as "actual monetary damages." Before September 2011, competitive injury was not required to bring a false marking suit. In fact, a plaintiff could sue any defendant for false marking on behalf of the United States (which is called suing "qui tam").
The Leahy-Smith America Invents Act amended the false marking statute by requiring competitive injury. It is not that difficult to show competitive injury, provided you have "standing."
Showing an intent to deceive is more difficult. False marking alleges fraudulent conduct, and fraud requires "particularity" in the complaint. Accordingly, a false marking complaint must explain the "who," "what," "when," "where," and "why" of false marking conduct. This is incredibly difficult before discovery, and jurisdictional discovery may be required.
Basically, you have to explain your allegations in more detail than an ordinary case when suing for false marking or fraud. If you do not sufficiently explain yourself and the false marking conduct, your complaint could be dismissed.