a. the person with feedback or background noise causing the video to flip to them
b. someone displaying their lunch for everyone to see
c. Zoom specialty: obnoxious video backgrounds
Zoom helps you block trolls, but does nothing for the pain of having to listen to someone's feedback during an hour long meeting. And you often don't want to interrupt the meeting to pester people about their microphone.
It's a similar problem to Slack. We have some people who overuse @here and various similar sins, and Slack's answer is there's no reason to block, just fix your company.[1]
What this misses is there's a broad range of behavior between pleasant and malicious. There are also a broad range of social remedies we normally use to deal with this behavior.
Most of those social remedies don't work well online. It's surprisingly hard to craft a written correction that doesn't come across as an attack, especially if you're senior and don't want to unintentionally throw that rank around.