So when you search for Wikipedia articles at mahalo.com, you get... Wikipedia articles at mahalo.com? The case would be stronger if you could show searching for "Foo" to come up with the Foo Wikipedia page at mahalo.com above Wikipedia itself.

This is incredibly hard. Most likely they won't rank for the exact same Wikipedia topic, but for more specific queries like "foo bar widget spam other term". Most likely due to the combination of all their scraped content. Google's duplicate content detection is definitely not rock solid and thats why these sites are working. For years in the past and for years to come.

So if a user searches for "foo" he lands on wikipedia, if he wants to get more specific and searches for "foo bar widget spam other term" he lands on the mahalo duplicate content page, again with the same content. Because user research (Don't make me think - Steve Krugs) has shown that if users do not find what they are looking for, they look for the fastest way out. The fastest way out is through all ads placed on Mahalo and thats why they make money.

I hope you and everyone else now sees that all of these pages who make a little impact on their own but a big one on the whole are decreasing the quality of Google's index. And because these terms are so specific its hard (and pointless) to point them out specifically. If you are in Google's index, you rank for some terms, else you wouldn't be indexed, this query conveniently points out all spammy pages on Mahalo so Google can take appropriate action....unless they actually give Mahalo a different treatment than all those other spam sites.