Jessica Kizorek does a nice job of breaking down our motivations for sharing information in this Online Video Insider article:
Why do people share video?
They do so because it reinforces and strengthens the bond between the sender and the recipient. When someone shares a YouTube video with his or her friend, there is a subliminal communication taking place: "You would like this because I know you and I'm in touch with who you are as a human being, and I want to provide you with something you'd be interested in."
In the business world, a viewer may send someone a video clip to educate or inform a potential client. He or she is effectively saying to that person, "We are on the same page. We should do business because you can count on me and I'm listening to what you need. You can trust me -- I know what's going on."
When a video clip is received well, it immediately strengthens the relationship. If the video is not relevant or inappropriate, it weakens the bond right there and then. The deterioration of rapport may be conscious or unconscious. Either way, the sender becomes either a resource or a waste of time.
Think, therefore, before you hit send. What's your motivation for sharing the link? Are you certain it will position you as a resource?