There is a thread at the Microsoft Advertising Forum with complaints from some advertisers over how to control where your Microsoft adCenter ads are shown.
Within adCenter you can also target sites for your ads to be displayed on. This is similar to AdSense but on Microsoft. The issue is, some are saying they do not have enough control to block certain sites. One advertiser said:
Previously we were able to exclude Microsoft properties from our ads appearing. Since the merger, we're no longer able to exclude some of these properties from our content network ads. This has caused a HUGE spike in my cost per acquisition. To a point of where I've actually had to shut off some of my campaigns I previously ran.
Microsoft support representatives are trying to help this advertiser. They suggested that they currently only offer exclusions for content sites not syndicated search sites. Not allowing exclusion in this case. But this in not the case, as the advertiser said.
So then Microsoft admitted that "there are certain sites that cannot be excluded in our website exclusion list." Obviously this enraged the advertiser, so the Microsoft once again tried to offer another alternative.
She said, "You have the option to create an adgroup distributed only to certain sites on our content network as well. Not all sites are included in this option but if you prefer you can create a content only ad group and bid on certain networks and websites instead of keywords."
I doubt this will make this advertiser happy. Bottom line, advertisers want complete control of where their ads show up.
Forum discussion at Microsoft Advertising Forum.