agent_x - 9:29 pm on Nov 15, 2011 (gmt 0)
Log file spam [webmasterworld.com]. Some log files are public. If they send out fake referrer information to your site, if your log files are public then that referrer information will show up as a link from your public logfile.
The process is indiscriminate. Often doesn't matter if your log files are public or not.
This isn't referrer spam, this is different (or maybe it's a more sophisticated form of it). These are links that googlebot is finding in a page that point to your site and is listing them in GWT. I can't immediately see the reason for doing it, apart from some attempt to give the page some legitimacy by linking out to established sites perhaps?