Shark Shield is a personal safety product designed to reduce risk, the same as a seat belt or bike helmet. Anyone not wearing a Shark Shield is naturally at more risk than somebody who is wearing a unit.
It has been scientifically proven that Shark Shield does not attract sharks, please see our FAQ on this here, so the fact that one person is wearing a unit does not mean that those around him/her are placed at greater risk than if nobody in the group was wearing a unit.
Your risk of an unwanted shark encounter is reduced because you are using a safety product designed to reduce risk. It would be a fair assumption to state that the more people wearing a Shark Shield the larger the probability that a shark will be deterred from the group.