Referer spam is kind of old school but because of that, many SEOs don't fully understand what it is. Referer spam is basically making repeated requests to a specific web page with the goal of showing up often in the referer logs and analytics. If web sites publish their referer logs, then that link in the referer 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.
Forum discussion at Google+.

Comments:
Brandon
02/06/2013 06:04 pm
That's an awesome shirt
Jeremy Meindl
02/07/2013 03:39 am
OMG so 2004
black hat team
02/07/2013 11:35 am
Excellent information thanks for share..@matt cutts awesome shirt
MonkeyMarcel
02/07/2013 12:30 pm
LoL, @black hat team giving Matt a thank you!
Dewaldt Huysamen
02/07/2013 12:35 pm
Wow ok that is something I never thought about. Hectic....
Local Search HQ
02/07/2013 12:42 pm
Haha nice t-shirt Matt.
CandleForex
02/07/2013 01:18 pm
Matt worried about Referer spam today in 2013? Haven't heard of this been used effectively in like 10 years?
SEO Consult
02/07/2013 04:41 pm
Mainly from the days before Google Analytics I'd imagine re: web logs published to site. If that was still common there'd be a great competitive advantage to be had.
Rank Watch
02/07/2013 06:08 pm
Matt Cutts the Google web spam team head is certainly an expert at explaining stuff in a simple and concise manner. Kudos Matt, you certainly deserve it.
Jayine
02/08/2013 09:17 am
Thanks for sharing knowledge about matt cutts...
Eyepaq
02/08/2013 11:32 am
indeed .. back in the days ..so 2004 :)) I didn't know that this is still around.