Patents seem to do a good job in general when it comes to protecting the original owner's interest in cases where the invention falls well within the traditional matter of patents: utility patents, plant patents, and design patents. Patent law generally provides good protection for "classic" inventions such as machines, devices, etc (i.e. tangible inventions). However, as we move from a manufacture/engineering-based economy towards the digital economy and the "service/experience" economy, traditional patent protection has limitations. In the past 50 years US firms sought patent protection for their inventions since manufacture and engineering innovations gave them an important competitive advantage. As the technology matures and global competitors can produce similar quality products at lower cost, some of the competitive advantage based exclusively on "tangible" inventions is more limited (Porter). Additionally, given that nowadays the US economy is primarily a "services economy" where even engineering companies that have traditionally focused on device manufacture such as IBM have shifted their orientation towards providing service solutions; protection in the area of business processes, software, and other more "abstract" and "intangible" inventions is becoming more important. While the USPTO have been shown to be more capable of adapting to accommodate this shift toward more intangible inventions than the EPO (European Patent Office), protection is still limited in many emerging areas.

References:
[1] Stim, R. "Intellectual Property. Patents, Trademarks, and Copyrights" West Legal Studies.
[2] Black's Law Dictionary 5th ed., (West Publishing, 1979).
[3] Manual of Patent Examining Procedure, 8th Edition
[4] The European Patent Convention
[5] Porter, ME. "Competitive Advantage".