IP entrepreneurs typically want to get, and should get, notification of their IP rights on their product, packaging, and marketing materials. The benefits are legion, from alerting people to the claim of right in the product, the product configuration, the product name, etc., to utilizing the advertising benefit of claiming a patented, trademark registered, or copyrighted creation. For patents, failure to properly mark can preclude the patent owner from getting any damages at all from an infringer. So to, the means for marking can be legion, from Patents: "pat. pending", "U.S. Pat. _", "U.S. Des. Pat. _", "U.S. Plant Pat. PP_", to Trademarks: (TM), (R), (SM), to Copyrights: (SR), (PA), (C), among others.
But marking has its flip side. To avoid a claim of false marking, there must be, as an absolute floor, a reasonable belief that the product marked as "patent pending" is actually the subject of a legitimate patent application, that a product marked as "U.S. Patent _" is actually covered by claims of a validly issued and unexpired patent, that a mark with the (R) subscript is actually registered by the U.S. Federal government, and not by a state or foreign country.
Where this floor is not met, the penalties can be stiff. For false marking of a patent, a Federal statute imposes a fine of $500 per product, and the suit can be brought by anyone, even if you don't have a dispute with them. False marking can also constitute unfair competition and violation of trade laws.
In short, marking laws can be complex. To do it properly, the IP entrepreneur must make sure to toe the mark.