If you are using Facebook social apps for watching videos, reading content and you don't want your friends or everyone to know about your activity, you can turn this off.
If you want to put your video files online using HTML5 then it's recommended to have three different formats for a full browser support. Those formats are mp4, ogv and webm.
In Photoshop CS6, the new version of Photoshop, you can use special cropping tool and you are done, but that doesn't mean you cannot achieve the same result with older versions.
