Yell Threatens to Shut Down Yellowikis

Yellowikis is a yellow pages wiki community, started by a dad and a daughter, with 500 editors collaborating on open business listings.  Now Yell, the world's largest yellow pages publisher, based in the UK, is threatening them to shut down.

Yell is demanding that Paul and Rosa close down the website, transfer the domain names to Yell and agree to pay damages to Yell for loss of profits. Yell made $2.4bn in 2005, whereas Yellowikis had a loss of $500. The $500 was used to print T-shirts promoting Yellowikis at the Wikimania conference in Frankfurt.

Now last I checked, yellow was a color, and yellow pages was a generic term.  Maybe that's why the Yell Group plc picked a more unique name themselves, but its hard to see the trademark infringement.  But as a small wiki community, its even harder to see them standing against the cease and desist letter.

UPDATE: Chuqui: "Yellow Pages is not a trademark in the U.S. It *is* a trademark in the U.K. That's why Sun's Yellow Pages became NIS. so they have a trademark issue in the U.K. here."  Contrary opinions in comments below.