ok so me and my girlfriend both have evo's. Mine and hers both started turning on speakerphone by itself in the middle of calls. It i pull the phone away from my ear it goes off then i put it back to my ear it turns on again. Did we accidentally change a setting? Hers is doing exact same thing.
You wouldn't have happened to download switch pro on both phones did you? This has happened to me a few times. A reboot will fix it, unless you have a toggle widget or app that can disable or enable the auto speakerphone.