As we mentioned last month, changes to negative keywords were starting to roll out to all advertisers. As of now, those changes are complete! Negative keywords uploaded at the campaign and ad group level will now be combined to filter traffic, working in tandem with one another. In the past, negative keywords at the ad group level would override those at the campaign level.
You'll find more detail on this change over on the adCenter Blog, you'll find more information for API users over on MSDN.
We are continuing our efforts to release the new unified behavior of Negative Keywords. We plan to increase coverage and participation until we have fully released this feature globally to all advertisers within all markets. Remember to check back with us for progress updates for this feature.