Why am I getting traffic from adf.ly?

[beavis]

Today, I was checking my traffic in Google Analytics. I normally get a very steady amount of traffic. However, on Dec. 25, 26 and 27 my traffic was 4x normal. This has never happened before. For years, it has been very stable.

Upon checking my logs, I note that the entire increase is from "adf.ly" Upon further investigation, I found a website at the adf.ly address that offers a "URL shortener" service with some sort of payment scheme. I have not signed up or utilized this service in any way.

Can anyone explain what may be going on? Is this traffic any "black hat" stuff that someone else may be doing to my site that I should worry about or block?

[tangor]

From their website comes the following (under you don't have to have a website to earn money):

Facebook. Got a great website to share with your friends? Shrink it with AdF.ly first.

Forums. If you are helping people out on a forum and giving them the answers they require, shrink any website URLs with AdF.ly and then include them in your post. Be absolutely sure you are not spamming though, otherwise you get your account suspended. Always abide by the forum rules.

Twitter. Do you have a Twitter with lots of followers? AdF.ly is perfect for tweeting links that will earn you money.

Anywhere you normally post links! Use your imagination and paid by us every month.

Looks like a link collecting biz... with US and UK sites per 1K paying the most.