Sounds like plain referral. To me, the key to the Dropbox system is that the referrer is rewarded with more Dropbox. This makes the recommendation more sincere. Another issue is that the Curebit referral seems to occur before customers have received the product, so they can't logically recommend it, in general.
Dropbox addresses my ethical concerns about referrals; Curebit doesn't (based on this submission).
The referral happening is just an action - so a SaaS company using it could easily provide credit, as with Dropbox. You could provide a callback URL for us to notify you when the referral happens, but we handle all the tracking, url generation, analytics, split testing, etc. Check out the custom integration instructions: http://www.curebit.com/integration#custom
Some of our stores (mypuppypads.com) delay the offer by a week - giving their customers a chance to first try the product.
In other cases, like when Six Orange Grove runs a Charlie's Soap deal (these always go super viral), there's no need to delay the offer. The people that buy & share are die-hard Charlie's Soap fans that stockpile it whenever it goes on sale: http://twitter.com/#!/kakaty/statuses/4377656799793152 http://twitter.com/#!/myfirstkitchen/statuses/43714330105036...
However... there is an intriguing idea that you might be more successful by only doing it the dropbox way. It seems counterintuitive to restrict your options, but then you really would be productizing the dropbox approach - you'd be offering not only the implementation of it, but also a guide to it, an explanation for why it works etc. Not technology, but valuable business guidance. It would also be simpler and more convenient, by being less customizable to use; and more definite and concrete in your marketing materials, making it easier to understand and pass on, and be stickier.
But developers hate artificially limiting their technology; and I'm far from able to guarantee it would sell better (or, indeed, at all).
I guess you could simulate it, by having a form/wizard, that guides the user through the issues of a dropbox-style referral - sort of like "referral model advice" - but one that ideally would also create the system on the spot! I'm thinking that many people have much less idea of referral programs than you do (and value their ignorance); making the choices simpler is a big plus for these folk. Of course, I don't know if referral systems are well-understood enough yet to be reduced to simple rules that always work (or work reasonably reliably, well enough for a first iteration for the client).
re: ethics, if we look at curebit as a platform that's encouraging more ethical referrals (by focusing on pre-built social network relationships and encouraging retailers to use best practices), we shouldn't expect them to have to limit their growth by forcing early users into unfamiliar patterns in order to be the moral police on anyone wanting to try their platform.
Now our product vision is to offer a small variety of simple models proven to work well, to get people started. But we also let hackers tweak stuff so it can work more seamlessly with their products.
Allan