Business ByDesign was a horrible, lackluster way of offering ERP under the SaaS model. I've used it - and I was absolutely disgusted. It could not compete with the likes of Netsuite when it comes to the SMB market.
I've thought long and hard as to why SAP is not offering a 'true' SaaS product - the main reason I think is still lack of customer interest. Most of SAP's customers are large to very-large companies who require a crapton of customization to their ERP and other core systems. Their internal processes are simply not standard enough and hence a strict SaaS play product is not a great fit for large accounts.
On top of that the whole sales process to large accounts is radically different (and 'old skool') with consultants visiting customer sites and planning implementations... very traditional. It seems to be almost required still for ERP. Customers don't just whip out their credit card to set up an ERP system. Yet.
SAP still does plenty in the cloud but most customer requests are for IaaS type cloud hosting. SaaS is not done right at SAP right now, whereas I still think they /can/ do it - they certainly have the brainpower for it. I hope development efforts will shift to a fresh product that will rival Netsuite and target the SMB market.
Although having said that - Netsuite's revenue and market share compared to SAP are still tiny...