No. All databases have a schema, whether they are explicit (i.e. traditional relational databases) or inferred (i.e, so called schema-less databases). Rigidity arises in systems to the extent that the schema pervades the storage representation or application access patterns, making changes to your tables or documents difficult. The schema required to encode datoms is extremely minimal, consisting primarily of the attribute definitions, which specify name, type, cardinality etc. The advantage of an explicit flexible schema definition is that it provides power to your system:
Power to efficiently access the data (via query)
Power to directly model the domain structure of your data
Power to reason about the representation of the data in the database
