Bryson Meunier posted a study showing that search results on a desktop different from search results on a smart phone by about 86%.
That means, the results you get for a specific keyword search when done on a iPhone or Android phone will 86% of the time be different in some way then if you conducted the same search on a desktop browser.
Bryson said that most SEOs have claimed there are no major differences between the two. I don't really remember respected SEOs saying that but maybe they have. I do know there aren't many SEO changes one should make between optimizing their pages for desktop versus iPhone or Android phones, specifically. Okay, this is an over simplification of the process and I've explained a lot what you should be aware of.
Overall, as Bryson said, the majority of the difference in the search results has to do with Google showing you more locally related results. Google feels, if you are searching on a mobile device, your search intent is more locally specific. He documented what he saw were the main differences. He said:
- Local results more likely in mobile, so Google Places listings sometimes appear higher in results than they do in desktop, and domains with local intent more likely to appear
- Positions of vertical results likely different in smartphone results
- Blended mobile ranking algorithm for mobile queries
- Android Market or iTunes results for queries that include “download” or “app”
- Brand and store filters don’t currently occur in mobile smartphone search
- If CTR and bounce rate data is used to determine ranking in smartphone results, CTR and bounce rate more likely to vary in mobile smartphone listings, as listings in search suggest, abbreviated title line breaks and descriptions, unusable desktop sites in mobile results, increased engagement of mobile users and the variations in ranking mentioned above are all likely to change click through rates and bounce rates for smartphone searches
Forum discussion at Sphinn.