When we pray for someone to be healed, we pray this individually in the Amidah but we also often have a community misheberach list. I assume that there is a theological reason for the public prayer, and not just to publicize who might need some extra support, especially since you probably have no idea who Plonit bat Shimon is without further context. (For men, at least you hear them called to the torah.)
Similarly, we often have more than one person praying (individually) for the same person and they know about each other. Do the extra pray-ers help?
What is the benefit to having more than one person pray for the same recipient, either through the public misheberach or through multiple people's private prayers? Surely God, who is just and merciful, would respond to a single prayer in a good cause, and, being all-powerful, does not need to manage a queue where popular requests are dealt with first and multiplied prayer "votes people to the top".
Does God care how many of us pray for a particular person? What is the effect of the multiplied prayer?
This question is prompted by this answer to a quastion about asking others to pray for someone.