Frankly, it is not worth the expenses or going the distance. Just ask Perfect10 who have been trying to sue everyone for years on how successful they have not/been. Especially when it comes to Google, and their 'chillingeffects.org'.
Once they received notice, they removed it per DMCA.
Them admitting it was used in an advertisement, and them intentionally or maliciously admitting to using it are two different things. Especially if it is just rotated their member's images based on click thru's or some shit by their CMS or script.
While they are trying to cite 'user uploaded content' and 'safe harbor' as on their side, I think there is simply too much grey area in this matter, and you are going to spend a lot of money and years of hassle for nothing more than pride.
There was a YouTube case just last year involving some dancing kid and a song playing in the background while the kid was dancing. The record company sued and lost. The video was reposted and legal. I would open up a history book, and bone up on some cases already lost before breaking open your check book to pursue this.
That said, "pride has no place in the courtroom".
