All files contain unused space. Some of this space is used for meta data. Open a Word document in a text editor like Notepad and you'll see that metadata. There is so much space inside some files (such as large image files) that you can hide entire documents in it.
So develop an app. that inserts detailed metadata into different file types in standard ways that your slightly enhanced search engine can read. You could sell this as a 9.99 downloadable, or charge a subscription for access to your enhanced search engine. Or if you are already rich enough, you could give it away for free.
As folk create their files, they process them with your app. that inserts any descriptive metadata they choose into unused space within the file. There are a number of additional techniques that you can use to prevent metadata abuse using this system. The files with this enhanced metadata automatically go to the top of your search engine's results, so everybody benefits.
Back to Stig's Dump.