We have one guy that works for our sister company that loves his speaker phone. I refuse to talk to him while he is one it, because he does not know how to use it.
His phone sits in the upper right hand corner of his desk and his computer is on a computer desk behind his big desk. He LOVES to try talking to you while he is facing his computer, instead of facing his phone.
Each and every time I get the pleasure of talking to him, if I can tell he's on speaker, and it's not that hard to tell, he ends up repeating everything he says 3 or 4 times. I have ZERO issue telling him during a call, I can't understand you or what was that you said. I have even told him to turn his chair around and speak towards the phone, not the back wall of his office. The girls in his office, have told me that I am the only person he almost never uses the speaker with any more, just because I call him out on it.