Different websites from gold farming websites contact you at the same time another does? How?

So we all get the spam from gold farming websites. But i've noticed that they all contact you the same time another website does. Which is odd.

kind of like this

VISIT WWW.BLAHBLAH.COM Then a different website VISIT WWW.BLAH22.COM

Why isnt it random? They someone how paired up? 0.o