I'm not outraged that people can do that with email because I know how email works at a technical level, and I'm comfortable trading that control for a standard decentralized communication medium that I understand the implications of. I do get annoyed when people actually do it, though, and that's why filters exist.

Facebook is different. They solely control the medium, and can actually fix it if people complain. Also, the implications are not as readily apparent as with email - this aspect was certainly not played up in the announcement yesterday - and posts like this help people understand exactly what's going on, so they can figure out how to use the system correctly.

And, really, if a feature isn't going to offer a meaningful improvement over email, why does it exist? "It's just like email" just tells me I'm going to keep using email.