Matt Cutts Explained Referer Spam
Referrer spam is kind of old school but because of that, many SEOs don't fully understand what it is. Referrer spam is basically making repeated requests to a specific web page with the goal of showing up often in the referrer logs and analytics. If web sites publish their referrer logs, then that link in the referrer logs is indexable by search engines. If not, webmasters may notice the spike in traffic, visit the web page and maybe think it is important to link to it.
Matt Cutts, Google's head of web spam, explained all of this in a short two-minute video:
Hopefully that explains an old school tactic in a nice concise manner.
Reposted from Search Engine Roundtable