Ideally it would be continually audited by multiple trusted third parties.. something maybe like the EFF.
Even then there'd be no guarantees, but it'd be way better than what users have now, which is just DDG's claims.
For a for profit company, the third parties such as EFF would be good enough for most users. Would highly recommend that EFF offer some sort of certificate (PGP signed key would be fine) to authenticate such audit.
While there is no privacy audit that I'm aware of, the theory is that there is no motivation to sell my searching habits to anyone.
DDG plans such a feature, but it will likely never be their primary revenue driver.
Two examples:
- While Neeva has no ads, they prioritize sites with tons of ads in their results (search for 'best laptop'). If your main premise is that ads are bad, why not penalize/remove second order sites that are heavy in ads?
- They claim they respect user privacy, yet make technical choices like using raw Google maps in their product as Maps module, which sends requests from the client directly to Google
They could sell your data for even more of a profit. Why couldn't that motivate them?
Or they could do it to comply with some jurisdiction's laws.
Or they could do it accidentally or as a leak from within.
The best protection is that no data is collected in the first place, but we need auditing to make the claim of no collection credible.
They have almost infinite ways of identifying my right to use their engine given that they're the one emitting the Open Search snippet from within an authenticated window; uuid hostname or uuid path/query param are the two which spring to mind