The disadvantage of using google+ comment on blogger

Google has give a new feature for blogger comment. That feature is google+ comment system but can be used on blogspot. Some of the advantage is the framework VALID HTML5, that's very nice for SEO (i think). But did you know?, the blogger commenter don't always have google+ account, some of people is just browsing and when wanna asking something, he must sign up or login to google, but how if the browser don't have google+ account?, they can't comment of course and you can't know what is their message and comment, so that's it, the normal visitor can't comment, that's the disadvantage....