On business websites, the photo is the over-rated. Some favor it since they believe a photo can turn prospective clients into actual customers. That is if the prospect likes the photo. My theory is the photo can only hurt you. If a prospect wants to patronize a business and the business possesses what that prospect wants, then independent of the photo, the chance of a prospect to client conversion is high. That person will buy from a business regardless of whether he likes a photo or not. Photos are seemingly effective if prospects have no high intentions of making a transaction in the first place. Under these circumstances, transactions can not be explained by rational decisions towards obtaining a dental service exclusively.
Relating to lowly sought businesses, if a prospect likes a photo that does not guarantee he will show. If he does not like a photo, the business has just increased the chances of the prospect not patronizing his business.
Relating to highly sought-after business products, my theory is the photo can only hurt you in these cases since the business model has already assured the prospect to client conversion chance to a high one.