Change from search terms to websites, and Google trends tells a different story: http://trends.google.com/websites?q=okcupid.com%2C+plentyoff...

My guess is googling for "okcupid" all as one word is relatively more frequent than "plentyoffish" as one word, and here's confirmation using Google Insights for Search, which allows OR queries:

http://www.google.com/insights/search/#q=%28okcupid%20%2B%20...

As much as the PoF guy's pontificating gets old to me, and agree with your Facebook-MySpace analogy, he's still killing OKCupid traffic-wise.