Ads depend on your location etc. We have had a discussion about this same example before and plenty of people got similar results: https://news.ycombinator.com/item?id=6533287 e.g. http://i.imgur.com/mhJhc5W.png and http://i.imgur.com/2iFv7Yf.png

And for what it's worth, this is the result I got just now in the UK: http://i.imgur.com/YHXngwR.png

You are a showing a handpicked example which is disingenuous and not representative of real user experience. You decided to include a one-time cookie message that pushes down the content and not include the actual search results which are further down the page. FWIW the visitor that used this query got a clear answer to what bitcoin is and I'm pretty sure that any of the "small businesses" that are advertising in that spot are not deserving to be the first result for that query anyway so no conspiracy here.

It could be because the plus500.co.uk is manifestly UK (and people saying otherwise are probably based in the US).

Yes, it's just an example. I'm sure there are other terms that get more ads in the US than the UK. The point isn't this exact search term, it's that there are combinations of searches+locations that return pages where the entire of the visible page is filled with ads or google content and you have to scroll to see any real results at all.

Interestingly I (also UK) got the same, except missing the ad about mining. Isn't this tailoring (presumably with some basis in the users' behaviour) a substantial part of what is increasing their revenues (thus share price)?

Try disabling the Ad Blocker.