Du Val's company has been running LinkedIn ads advertising its services since May 2013. At first, they used stock photos, but by mid-July, they replaced the stock photos in the ads with real photos of their own engineers and developers, both male and female.
LinkedIn, however, pulled their ads because the "women ads" were not appropriate. Specifically, the ads showing screenshots of female engineers just looking at the camera. Here's a screenshot from Du Val's post:
UPDATE: According to Du Val, this photo, which he included with his article "by mistake," is a stock photo. The company, as stated earlier, originally used stock photos, then went to pictures of the actual engineers. Du Val takes issue with the fact that this stock photo, considered objectionable, is no different from the pictures of his own engineers — people dressed nicely, looking at the camera. His concern, it seems, is that the stock photo showed a pretty woman, and LinkedIn decided that pretty women and engineering don't go together.
Says Du Val:
We’ve taken extremely professional photos of both men and women who are part of the Toptal network and made sure they looked sharp, well dressed and happy; however, LinkedIn’s internal advertising’s staff completely disagrees that they both look sharp, well dressed and happy. Actually, they believe, with 100% certainty, that the women in our advertisements are offensive and harmful to their user base. To me, this is unbelievable.
Du Val's full piece In Defense of Female Engineers details the entire incident between Toptal and LinkedIn, including recent devlopments in which LinkedIn re-activated the ads.