Likelihood has to be judged against the evidence. A lot of scientifically-minded people have tested it for themselves and found ads to appear when they spoke about subject explicitly to test whether ads would appear. I recall several specific cases. It's not quite scientific enough for me, but I'd expect a scientific study to have the same conclusion.
Just like if you do a scientific study of whether baked beans make you toot, yes, you will find that they do.
Although you state there is a high likelihood of a false negative, it would be a useful study for me and others in the more likely case that it matches the informal n=1 studies numerous technical people performed by themselves.
