The domain FreePornTube.com sold on NameJet.com for $34,800.
The domain which seems to have just a little traffic, with an alexa ranking of over 1.5 million.
As a buyer of adult domains, it seems like a steep price to pay unless you own porntube.com (which has a tons of traffic) and its a defensive acquisition.
Moreover, porntube.com is a registered Servicemark.
We will see if this one stands up.