It's a very interesting question. I've long felt that Dreamhost's "unlimited webhosting space" policy will turn out to be untenable when a more substantial number of customers start doing what you are doing. Their current let-out ("not for archive/backup") will not allow them to honestly exclude customers such as you, unless they start telling a much better story about what they mean by "archive".
They could perhaps argue, for example, that your website is really a front-end to a large archive of multimedia material.
But such arguments will always be a matter for judgement-calls on a case-by-case basis. That is a really unsatisfactory way of running a webhosting business.
Far better, I think, would be to abandon the "unlimited" nonsense and institute a fixed limit of say 100GB or 200GB.