Another company is getting into the trackable ads game: Adobe. They’ve announced a new product: PDF files with ads. Publishers can upload PDF files to Adobe’s web site; the files will be modified to display ads via Yahoo!’s advertising network. When the PDF file is viewed, "contextual ads are dynamically matched to the content of the document." The ads are displayed in a sidebar; they aren’t printed, and don’t obscure the content of the document.
There is one bright spot: at least in the current version, users are shown a "network connection dialog" before any ads are retrieved. If you say "no", you won’t see the ads and you won’t be tracked. You can even select "Remember my action". Frankly, I suspect that that won’t last; given a choice, most people will decline to see ads. Time will tell; for now, I applaud Adobe for including that feature.