With more recent (last 2-3 years) Google algo changes, link profiles have become an issue, where they were less so before.
Which means that when looking at more 'aged' domains/websites, the telltale signs of backlink software and comment bots are frequently there (or some other form of mass backlink creation), regardless of whether it is a decent site with good content, or a short term money maker with poor content.
I'm not ready to buy anything yet but I regularly run 'interesting properties' through a due diligence routine - which includes link checking on ahrefs and majestic, domain analysis on seomoz site explorer , etc. And I frequently find even the 'good looking properties' have poor link profiles (too many links from India, Asia, Russia and S America when they are English language sites, for example), often with too many links coming from too few domains. And a check on seomoz often reflects this state of affairs wiht a low 'moztrust' value and page/domain authority.
Google PR is, apparently, becoming obsolete, so PR 4, 5 and 6 domains are not necessarily the golden chalice they once were, and things like moztrust and link profile/quality may be a better way to estimate the authority or perceived quality of a prospective site - in an attempt to second guess MR Google, that is.
So what value/weight do you place on these things? Given that good quality link profiles take a hell of a lot more time and money to build than poor ones, how confident can you ever be that you can turn an established site's profile around before it, potentially, sinks into oblivion under?