With HBase, you have to be very careful when using column families. Too many and performance goes out the window.
This is due to compaction and splits.
With respect to MapRDB, you don't have compaction, so then the question becomes what's a realistic limit on column families.
In some use cases, I've seen RDBMS tables placed in separate CFs using a common row_id to effectively create a record view. Is this a stable use of CFs vs placing the rows in to the same CF?
Note: This is where MapRDB diverges from HBase and what would be a Best Practice for MapRDB would not be a best practice for HBase.