OK. I thought you were getting it confused with one of the message saving snapchat proxies (which then got hacked). But whatsapp is clearly not a replacement. snapchat may have failed to delete videos from the users device, but whatsapp doesn't even try.
WhatsApp used to even save snapshots of the database, for a week(?) I believe. In a SQLite DB. And deleted messages are not vacuumed. Recovering intentionally deleted messages off a user's phone was a trivial job. At least on the Android version.
