Desktop apps with built-in ads are okay. I've used a few here and there. I've also seen shareware model software that has ads that can be turned off by register

Desktop apps with built-in ads are okay. I've used a few here and there. I've also seen shareware model software that has ads that can be turned off by registering. That's fine too. In this case the ads are part of the application. They live within it. Uninstall the app, and the ads are gone. Such ads also tend not to invade users' privacy outside the app. They might send stuff about what you do in the app, but if you don't like it you can uninstall the app. One of the key words here is "toolbar." It's in the same class as "HIV," "ebola," "herpes simplex virus," etc. Saying you're bundling third-party adware such as toolbars and "browser helpers" and similar is like saying you're purposefully giving someone a disease. IT professionals managing Windows networks spend god-awful amounts of time removing such junk from Windows PCs. Not only do things like this invade privacy, they often slow down and break peoples' computers.