Edit: 2. Does your online stuff give an accurate impression of you? Does it give a hire-worthy impression of you? Is it set to "private" or something similar?
3. Let's say you have a candidate who has the right qualifications and good professional references. What would you have to find on their online stuff to refuse to hire them?
I kind of think it's unfair. Yes, obviously posting stupid things about yourself on the internet is stupid, but employers in the past managed to hire people without prying that much. A person will act differently in their personal and professional lives, and it'd be more relevant to check their professional references.
2. Yes, and yes (though I still don't want employers to see it), and yes.