Google has removed the ads from the right side of the search engine results page (SERP)
On some searches you will see 4 ads at the top of the page instead of the previous 3, and you may also see ads at the bottom of the page, below the organic listings.
At the time of writing this it is thought there there will be up to 3 ads at the bottom, making a maximum total of 7 ads per page.
The right side had historically contained up to 8 ads, with a further 3 at the top of the page.
So with this change Google has dropped the total number of ads per page from 11 to 7.
We can only assume that Google Adwords could become more expensive, as bidding wars may take place for the important top 4 slots.
Organic listings will be pushed down slightly due the the forth ad at the top, but there is also a chance the organic traffice may increase with fewer ads on the results pages.