[jefftk]

Subpoena their records for a lawsuit and see what they really have. My prediction is that at major tech companies (Google, Facebook, Amazon, etc) your data is actually deleted when you say "delete" while startups tend to start with soft deletions (less worried about being sued).

[edwintorok]

It could be that they store your data all encrypted, and when you want it deleted they just delete the encryption key from a few well defined places. That way there is less need to mess with backups, etc.