I had it on for one of my retail sites when searching for the brand name/domain name. 10 results of mainly pages I'd been on-site optimising for along with a few deeplink product pages. This lasted for about 3 weeks and has now dropped down to displaying 6 results, all of which are my target pages.
I'm thinking that they may run 10 to test CTR and bounce rates then reduce down to the best performing.