Do you provide any kind of guarantee (perhaps an optional one, at the user's request) that you will delete/scrub any & all data you gather from/about a user at any particular point in time (say, after you're finished opting out everywhere, or after they delete their account)? Or will you keep that data indefinitely?

i.e. (how) can you assure users that this isn't yet another business actually trying to collect their data? It's kind of hard to do that unless you guarantee you will lose any data related to them once you've finished performing all the opt-outs on their behalf.