Would Whipser cause too much traffic?

miaozc

I'm thinking on the design of a pure p2p calling system using Ethereum and Whisper. So each node would need to register a unique "topic" name, and in order to call it, other node has to post some message to that topic. I'm wondering, would all nodes receive all these whispering, if so how can the system scale imaging receiving all the irrelevant whispers of other calls, not to mention problem of privacy?