Either way I'm not personally comfortable with this method since I often run servers on my personal computers for development. So whether it's 127.0.0.1 or 0.0.0.0 the request will still reach my system and possibly be handled by any port depending on who makes the request.

I would much rather have a browser plugin for this.

Those servers could be anything from MySQL, redis to any web app.

I get that the hosts-method is meant to affect all apps but that's not a big problem for me running Mac OS and Fedora.

Last time I had to block ads this way was when Opera had them embedded and it was much less memory hungry than Phoenix on my 256M RAM laptop. Back then I blocked them in ipfw instead.