HBase does not have any limit on the column names cross multiple column families. For instance, if you have column family 'cf1' and 'cf2', you can have the same column name in these column families, i.e. 'cf1:col1', 'cf2:col1'.
However, this is not allowed in cascading.hbase. If you try to create such scheme, cascading.hbase throws an exception. This should be allowed since it is a very basic usage.