In Cassandra, it's not recommended to have more than a few thousand column families, let's say 2,000 for the sake of argument. In cases where more than 2,000 types of data need to be persisted, one approach would be to shard multiple unrelated types of data into each column family.
For example, a single CF could contain Orders, Invoices, and Customers, provided their row keys were distinct (e.g. prefixed with the object type, i.e. the keys of a single CF could include both
Customer|1234). A second CF could contain say Addresses, LineItems, and OrderTypes. Given the basic feasibility of this approach, what are the practical limits on it? For example, what would be wrong with putting all 10,000 types of object into a single CF? As far as I can tell from the Cassandra wiki, there is no hard limitation on the size of a CF.