On Google plus, if gives you the option to mute posts that are spamming your notifications. Like, if people are having a conversation that you are not a part of, you can mute it, and if you wanted, you can unmute it later.
On G@G, sometimes the tagging can get out of control, and can result with you coming back to hundreds of notifications in your inbox. Wouldn't it be nice if you could mute your post until it dies down? Or if someone was spamming your opinion, would it be nice if you can mute it, instead of blocking the person?
I think it's a good idea. I haven't had too much of an issue with it, but it'd be nice since I'm sure you don't really want to block (most of) those people indefinitely, just not pay attention to their conversation.