YouTube's enormous size explains why search results can be different for different users. YouTube's collection of videos is too massive to be stored at one facility. YouTube stores all of its videos at specific locations called "data centers" that span the globe.  So say you work with a local DC video production company and upload your first marketing video to YouTube. Where does this video go? YouTube will decide, based upon location and other factors, which data center will store your video.

When someone performs a search in YouTube, the search is analyzed and then sent to a specific data center. For instance, one person in Virginia and another in India could search for the same term "baseball" but get different results. Location alone could account for the different search results as different data centers may be searched.  However, location is not the only factor that determines search results and where data gets stored. YouTube has not fully disclosed what these additional factors are, but it is likely they consider the IP address, browsing behavior, and tracking cookies of the user.

It's no wonder that the answer is complicated- YouTube has to manage an additional 48 hours of video uploaded to its data centers every minute!

Works Cited:                http://www.vaughns-1-pagers.com/internet/google-data-centers.htm