Having a data structure with an entry in it is not the same as knowing something with an acceptable level of confidence.
This is basically automated Chinese whispers. There's no sanity checking, no peer review, and no reality testing.
Here's one where absolutely NOTHING above the fold is a good idea. http://imgur.com/a/RXABg
Play stupid games, win stupid prizes I suppose.
However, I don't see the logic in picking one of them and highlighting it. It has the appearance of an endorsement.
I would also argue that the ads are deceptive for this query. Surely there's some AdWords policy about that?
But just a few years ago, Google's ads would appear in a sidebar, clearly separated from the search results content.
Not everyone is able to tell the difference today, and I think Google exploits this. I recently activated a new B2B website for an client and the senior manager was an older gentleman in his 50s. He never uses the browser address bar to navigate to websites, preferring instead to use the Google search box on his homepage. He sent me a panicked email saying when he typed in the new website's name, the Google search results showed competitors' names ahead of his. This was well after Google had crawled the site and it was showing up on the results page.
As it turned out, he did not understand that the first few results he was seeing were ads. While he isn't a savvy user, I would wager that many, many people are similar to him in that they don't exercise good judgement when they're on the web and would easily be fooled into thinking that something like "proton therapy" is a cure for cancer because it's at the top of the search results.
http://static1.businessinsider.com/image/4f2992c7eab8ea28690...
The point that they've slowly made changes over the years to make the ads look less like ads is very clear though.
They've also generally done a lot of work to push the organic results down. It's very easy to find queries where there's no organic result showing above the fold, even on a fairly decent desktop monitor.
That screenshot is pretty shocking. That's an insane amount of pixel space dedicated to the ads, then the Google featured snippet and finally the actual search.
https://physics.stackexchange.com/questions/169665/dose-dept...
I guess the main problem is with voice search, since you only get the one result.
Proton beam therapy is not widely known, which might explain the scare quotes in rchaud's comment suggesting that non-savvy Google users "would easily be fooled into thinking that something like 'proton therapy' is a cure for cancer because it's at the top of the search results".
I detest ads, so it feels weird to write something like praise for this one. I guess I dislike quackery even more. Now I want to try similar search queries to find other cases where a Google ad suggests a real treatment amid all the bullshit in the non-ad search results.