This is not a correct observation! Memcachedb is nothing but Memcached with BerkeleyDB underneath. Distribution of data in Memcached(also MemcachedDB) is achiev

This is not a correct observation! Memcachedb is nothing but Memcached with BerkeleyDB underneath. Distribution of data in Memcached(also MemcachedDB) is achieved by client side hashing of keys. If your argument were true then, Facebook would not scale vertically - they are the biggest users of memcached. MemcacheDB can be used in exactly the same - and we have in production BTW.