I don't know the details of the Campag / Shimano / Yeti relationships or personalities but I thought that Parkers honesty in covering up the Campag sticker contrasts with what most manufacturers do, which is to rebadge another brands product as their own. Just thinking of the full page Specialized adverts in road bike mags showing Tom Boonen in full flight on a range of products from Campag, Ambrosio, San Marco, Veloflex which are covered in 'S' logos.
In cases like this I don't think there is much the minor brands can do about it. I guess they are just happy to see their parts on winning bikes.