Simply put, the promo codes are all part of the Dreamhost rewards system. Dreamhost pays existing customers $97 for each new customer they refer to Dreamhost.
Now here is where it gets interesting, Dreamhost allows customers to share this $97 reward with the person they are referring. They do this by allowing customers to create their own custom promo codes.
When creating the promo code, existing customers can decide how much of the $97 reward payment they want to give to the new customer as a discount and how much they want to keep as a rewards payment.
For example, some people have decided to offer a $50 discount with their promo codes. If a new customer uses such a promo code they receive a $50 instant discount on their hosting and the promo code creator receives a $47 rewards payment.
Others (like me) have decided to create promo codes offering the full $97 as a discount.
Dreamhost limits the max discount that can be offered by a promo code to $97 for 1 year and 2 year plans and somewhat less for monthly plans, so even those who offer the full allowable discount will still receive some rewards payments for monthly signups.
No, it is just Dreamhosts way of encouraging new signups.
Pay just [color=#CC0000]$22.40[/color] for 1 year Dreamhost hosting, use promo-code [color=#CC0000]MOJO97[/color]
Save [color=#CC0000]$97[/color] on all 1 and 2 year plans!! (Max saving on monthly plans too!!)