I have many brides ask me if they really need to hire a videographer or if they can have their family member or friend do this?  My suggestion is always based on past experiences.  I always refer the client to examples of video taken by family, video taken by 1 camera professionally done and video taken by 2 cameras professionally done. I strive to obtain the best quality of work for each client and will lean towards hiring a professional, but at the end of the day, it is up to the client as to what is important for their day. See this article written by a videographer:

http://www.bealecorner.com/wedding/FAQ.html