I'm attempting to avoid engaging in your main point, because it would require taking notice of the accusation of fraud.

Fair enough. I hope I've been clear that my purpose here is not to single out AR or direct any criticism at you personally for how you run your business. AR is hardly the only place on the Internet, or indeed in bricks 'n' mortar stores, that says one thing in big letters in its marketing and something rather different in little letters on its terms page. I'm just giving an existence proof that this happens, to counter the position that customers of SaaS businesses should have no expectation of continuity from month to month just because someone's terms of service say there are no guarantees; I consider that argument unrealistic, and therefore a weak counter to the suggestion that customers might reasonably be upset when a service they invested in integrating and may have come to depend on in practical ways was bought out and shut down because of something like an acquihire.

There is an interesting discussion to be had about the best way to deal with the inevitable conflict between giving a fair but inevitably brief and informal description in marketing and having full and legally appropriate terms for actual contracts. This is something I've talked about several times with lawyers, and we generally have a somewhat different strategy to many US companies in this respect, but then we're not in the US and the legal climate here in the UK is somewhat different as well. I do understand that as someone posting with a well-known identity you might not consider this a suitable venue for such a discussion, interesting as it might otherwise be for all concerned.

They don't ask for AR's continuity plan, for the same reason they don't ask for their accountant's continuity plan, or their lawyer's continuity plan, etc.

Sorry, but I think that is not a fair comparison. I don't know the specifics in your jurisdiction, but it is common for professional standards bodies to require basic business continuity arrangements for accountants and lawyers of any level and dealing with clients of any level, and in most places in the first world these are regulated industries where it is literally unlawful to practise without holding the relevant qualifications and complying with the relevant professional standards.

So, if Dr. Carter's favourite accountant is taken ill and unable to continue working, it should be straightforward to transfer the necessary information to another accountant and have them take over with minimal disruption. The ability to file the doctor's accounts isn't just going to disappear overnight because the principal at the accounting firm got hired in a senior position at Deloitte.

There would normally be no need for Dr. Carter to spend crazy money on a Big Four/Five accountancy firm to ensure this basic level of protection. (This is rather fortunate for everyone else in the accountancy business.) Of course larger organisations with more demanding requirements involving many hours of work from whole teams of people on both sides might want stronger guarantees from the larger services organisations they deal with, and those will usually be available from the larger services organsations, and there will usually be additional fees involved. But approximately no-one who's using the kind of SaaS offerings we often discuss on HN is operating on that scale and at significant risk of the entire company providing the service they rely on being subject to an acquihire.