"...but is permitted to keep US communications where it 
    is not technically possible to remove them..."

That's a pretty big loophole that incents them to design future systems where it isn't "possible" to delete the data, where possible is likely to be interpreted as a gargantuan task or where data that should be deleted is so intertwined with data that isn't that they say they can't delete data without corrupting data they aren't required to delete. Many if not most NoSQL data stores are likely to be argued as impossible to delete because of the denormalization of data. Requiring them to only develop future systems where data is 100% guaranteed deleteable should be a legal requirement. (Fortunately this same requirement would also make indiscriminate dragnet big data analysis prohibitively expensive and slow)