>I'm sure that fifteen years from now, DuckDuckGo will be ad-infested crap
In terms of direct ads, perhaps. But for SEO spam, in many cases, DDG already seems to be there. For example, things as simple as "python datetime", "python json", or "python datetime.now", where it would seem obvious that the top result would be the documentation for the module/function, have spam sites above the actual Python documentation. Meanwhile, search for "matplotlib", and your screen will fill up with ads.
Even DDG knows that it can't handle everything, and so it has its bang shortcuts. I've used the !reddit one, and I'd use !w (Wikipedia) except I do those from the Firefox search bar.
I've heard the "everything's a bot" theory before, but never saw a name put to it before. I'd have to guess that 99% of all SMTP traffic is spam at this point.