Apple has filed a few patents recently that have eyebrows raised. There was the 3D display and user interface, and the 3D camera. As Shaylin Clark points out, having those patents on the books doesn’t even remotely mean that Apple intends to use them.

Apple could just be exploring possibilities for future designs. Securing a patent allows them to do that while keeping that technology out of the hands of competitors. Even if Apple never produces the product, they hold the patent and could have recourse if someone else builds it.

Another possibility has to do with the value of intellectual property. Sometimes companies register patents and sit on them just to drive up the value of their company. It’s almost like inventory. In fact, companies are bought and sold simply for the patents they hold. When the E.U. approved the Google buy of Motorola, it was widely understood that the 17,000 patents and 7,500 patents pending that Motorola held was a big part of the deal for Google.

Apple owns many patents, and it remains to be seen just how many of them will ever see the light of day. These includes such wonders as:

Apple also has to watch its back over patents owned by others. A company called Touchscreen Gestures LLC is suing Apple for patent infringement over certain touchscreen technologies that they had patented. That company is also suing HTC, Samsung and RIM.

Social game maker Zynga was sued over patents that another company claims to hold. Personalized Media Communications filed a patent suit in the U.S. District Court for the Eastern District of Texas against Zynga. They claim that the social games maker has infringed on four of their patents.

Apple itself has sued Motorola and Samsung, and been sued by SmartData.

A company called Smartphone Technologies tried to sue Amazon over technology in the Kindle Fire. The reached some undisclosed settlement with Amazon that kept the whole thing out of court.

One company claimed to hold a patent on the entire interactive Web. They filed suit against over a dozen companies, including Google, Amazon and Adobe. They lost.

Over the decades, lots of outrageous things have been patented. Many never saw the light of day. We wonder how life would be different if items like these had ever actually gone into production: