Content-Rich Doorway Pages
via seomoz.org
"You buy these existing domains--perhaps they already have a bunch of juicy links to them. You HTTP 301 redirect everything from those sites to your main site, www.xyzsignals.com. Cool, right? Free link juice, immediately!
Not so fast...Google's ahead of you on this, and is looking for people who do this purely for SEO benefit. Matt Cutts is pretty clear on this in this video."
