If your invention is worth money, there is a high probability that it is being manufactured, distributed, and sold either in this country or abroad.
An infringement search will try to locate activity that violates your patent rights using search engines, commercial networks (i.e. eBay and Amazon), blogs, video sharing sites (i.e. YouTube), and other websites where an infringer would try to market your invention.
Energy Example
Assume that your invention is a way to save money on gas. It is a modification to use less fuel in a car engine compared to other vehicles. What stops an auto parts manufacturer from reading your patent on the USPTO website? That company could start manufacturing the part and market it on the Internet. They could even enter into a contract with stores to market the item on a shelf, or through mail-order.
In today's economy, methods to save gas is not uncommon or an immediate red flag. But how do you know whether this part was built or designed with original engineering work or copied from your patent?
A search would focus on advertisements that target the cost of fuel. This shows what products are on the market. Your drawings could be used to compare a product to the actual patent. Technical analysis will be crucial as to how the part works.
Imagine the number of websites where methods to save gas are posted. Any one of these sites may have listings that infringe your valuable patent.
Handy Tool Example
You just invented a new tool. Perhaps for the garden. It might be a new shovel design that makes lifting dirt or snow easier and less harmful for your back. Most likely, it will be a simple design and easy to manufacture. It might be as simple as a handle bent with a certain curvature.
Such an easy design could be made in a garage. One photo and a description is all it takes to make a sale on the Internet.
What if the invention is a new shovel to mix cement? It looks like a standard shovel with holes, side rails, or angled grooves to make mixing an easier job. If a standard off-the-shelf shovel could be cut in such a way to copy your design, think how easy it would be for any garage hobbyist to start selling your invention.
It may be very difficult to locate this infringement. You would have to look at pictures of every shovel for sale, online and store shelves, in this country and abroad.
Big Business Example
What if a big national chain sees your invention and says "What a nice product. Lets make it." This company has its own brand. They simply submit a design to the factory and start manufacturing your idea under their name. Soon it will be on the shelves of a large corporation with a steady stream of customers 24 hours a day. A search will try to locate online catalogs where your product is listed under another name.
Computer Software example
Software is patentable if it produces a useful result. Lets assume you invent a new search engine method that indexes websites in a really creative and efficient way. What stops another search engine from using your process? How could you ever find out?
You have to analyze how each search engine indexes a site. A secretive company will not disclose infringement to the public. All you could do is determine whether there is any special functionality that resembles your process (i.e. displaying the number of unique pages and graphics on a particular site).
Recent Cases in the News
Verdict against Apple for $31 million in damages for infringing Qualcomm patents. This involved how iPhones quickly connect to the Internet along with extended battery life.
Apple was ordered to pay $506 million in damages to the Wisconsin Alumni Research Foundation. The University of Wisconsin-Madison had conducted research that Apple included in its own processors.
Blackberry sued Twitter for patent infringement for Twitter's operation of the main app and the advertisement platform.
Apple and Samsung have been engaged in litigation for several years regarding the iPhone's design and software features that included double-tap zooming and scrolling. A jury at one time had ruled that Samsung had to pay Apple $1 billion in damages, an amount that was later reduced.