The BBC reports on a proliferation of unfortunate ad adjacencies on social networks. First, it reported several brand marketers in the U.K. were pulling out of Facebook because their ads appeared to content from the uber-right British National Party. That followed an earlier story in which the BBC called attention to marketers whose ads were appearing next to videos of street fights on YouTube and other sites. The advertisers said they were unaware of the awkward placements as the ads were placed through blind networks. It will be something to watch as ad networks and user-generated content proliferate -- and advertisers increasingly tap into them to satisfy the need for scale. Do you know where your ads are showing up?