Well, for one, someone mentioned guest-posting. But then, guest-posting where? What if the blog is iffy? Would PA/DA give a solid indication of this kind of thing?

Or, for example, I know to stay away from "buy 40 bajillion backlinks for $3" and such, but what about an offer for an individual backlink from a high PR page, manually added potentially in the context of a guest post? Part of me thinks "okay, seems reasonable", but part of me thinks "if this is being offered then could the fact that it's being offered to others then pose an issue based on the appearance of high volume"?

Also: if there is the potential for "negative" SEO, wouldn't this be easily abusable? What's to stop me from blasting 60000 backlinks to one of my competitors?

That is, it looks like a whole bunch of sites got smacked around the penguin/panda updates, but is this by virtue of actually being hurt by google's algorithms, or by virtue of simply not being helped "as much"?

That is, was it a matter of the sites just not having any 'quality' backlinks, having relied on things google no longer liked, which would result in not having as much to push them to the top? That is, they would have been in the same position had they not had those shoddy practices?

Or was google actively punishing those sites? That is, are they worse off for having those shoddy practices?

I guess the reason I ask is I'm somewhat terrified of going "out there" to get backlinks -- worst case scenario: would it just not do much to help, or would it actually hurt?

Thanks!