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I'm rather new to this, and while I'm getting some sense of everything I'm trying to figure out what kind of scope of work lays ahead of me. The keywords I'm looking to rank for are "moderate difficulty" -- somewhere between the 45%-55% "difficulty scale" on seomoz's keyword difficulty report. Assuming I have a number of "A-grade" (according to SEOmoz's reports) optimized pages for these keywords, how many links of a given quality level should I be looking at building up? I mean, of course, the more the better, but if I'm gunning for high DA/PA pages, am I looking at dozens here or hundreds of such links? I can imagine that any answer isn't going to come with much specificity, but if there was just an "idea" of the scale of backlinking involved here, that'd be great!

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!