Miss Manners: Is it rude to talk on one's phone in a public place?
Speaking loudly on cellphones in public and monopolizing conversations with self-focused topics are rude; good manners require considerate volume and reciprocal exchange.
When It's Acceptable to Be on Speakerphone in Public
People often use speakerphone in public, imposing loud personal conversations on others in inappropriate settings like hikes, elevators, restaurants, and gatherings.