"The question is, would this kind of thing be good (certainly it would help to build trust in the brand), or would it potentially be too much of a distraction from the ultimate goal, which for an affiliate is getting the visitor to click on the link and fill out a lead."
My feeling is that if it's COMPELLING it will help get the customer to the merchant to take action. Especially with a product that has emotional impact like that one does. I can't imagine a text link or banner could pull someone in better than a video of a mother saying how much it helped her.
Or better yet a cute little 2 year old saying how happy they are that Mommy and Daddy were 'smart' enough to get the maternity card!
(if they use that last idea tell them I want a cut of the millions they'll rake in!)
If you just offer the video as one option for creative, then affiliates that know their audience will like it and have room for it will use it. Others that just want a banner wont bother.