Not so long ago Google discounted the backlinks of websites that had dropped and changed ownership.
Now I am seeing sites from the same webmasters reappearing in a similiar format update after update:
1. Buy an old established website that has good google value. 2. Take ownership BEFORE the domain drops. 3. Create an unspammy directory with thousands of pages with overture or espotting results. 4. Wait for an update and hey presto you are everywhere. 5. After two to three months you'll get banned, so make sure you have already started step 1 with a new site.
I have seen this happen so much recently and by the same webmasters, one of whom registered the new domain in a relatives name so as not to get noticed.
Perhaps Googles new army of quality controllers will eek this out quicker - I hope so because it isn;t happending at the moment...