Business by Design for SAP is something very unusual.
Firstly, in some ways it's a first with a "traditional" software house rolling out a "cloud" solution. All the existing SaaS providers are that and nothing else, so all credit to SAP for venturing into this space.
Secondly, Business by Design presents an interesting option for existing SAP users, as it offers the opportunity to buy into areas that frankly would never fly locally in small-scale implementations, purely because of hardware and staff resourcing. The beauty here is that it offers great integration from SAP ERP to SAP Business by Design.
You should not underestimate the amount of experience that SAP has gained in the enterprise world. It knows that in fully using an enterprise solution every part of your business is impacted and this is where the dilemma starts to surface.
Everyone always quotes salesforce.com as the one to watch in the cloud space, and yes it's no doubt good at the sales and marketing side of the enterprise, however that is just part of one of the core business processes - order to cash; and actually it's mainly about the order.
In some businesses, especially service-related businesses the order component is absolutely the most critical and in some cases the major part of the business activity.
But let's think about a manufacturing company where getting the order is the only the first part. Then they have to procure the parts and services, assemble it, package it, deliver it and get the money for it.
We shouldn't forget they have to do that safely, on time and to budget, while at the same time looking after their staff and maintaining their premises. For a public sector operation, such as police force who have customers (albeit another sort!), they have police cars, buildings, and people to look after as well.