dstiles - 10:57 pm on Mar 25, 2011 (gmt 0)
In the domestic service and information categories I would say more than a few links were indicative of "illegal" link building. Most people browsing sites in those categories simply do not have a web site to put links on, so discounting FB/Twitter as "real" links there could not really be more than a few links to those sites. Hence if they have thousands or more G should certainly be looking closely at how they came to get them. That IS spam.
Google screwed up links as a currency anyway: it used to be "I like your site, I will link to it: if you like mine please link back." In recent years I've been spammed senseless with "Link to us three ways" and "We will build links for your site".
Links mean "authority"? Links usually, in my view, mean "spam".