Also if DuckDuckGo can target you based on what you're searching there and then, is that not targeting? It's not stalk based targeted advertising, but you're still an ideal target since they're showing you something you're searching for, in some cases it might not be fully relevant to what you wanted, but close enough to be shown (not sure how highly relevant DuckDuckGo ads become relative to search terms).
For example Apple could infer categories of users according to their Appstore profile and permit you to target people by their trade.