Just a few random thoughts:
- Storing objects as blobs in a database makes it (nearly) impossible to do useful searches in them. Since the power of SQL queries is the main selling point of relation database systems, that's really a pity, and you might want to consider other storage systems ("nosql")
- If all your objects have similar structure, storing them in a proper schema would improve searchability
- YAML doesn't capture all features of Perl 5 data structures (for example weak references).
- Storable captures more features, but you'll generally have problems changing to a different version of Storable (or Perl, for that matter).
- If you plan to support multiple serialization formats, store the format in addition to the actual data.