In my previous post Does ERP matter? I discussed the business requirements for enterprise resource planning - a management style involving tight command-and-control coupling between different enterprise functions (sales & marketing, distribution, manufacturing, purchasing).
However, this is not the question addressed in Shai Agassi's original post Does ERP matter? His primary concern (as it has been for much of his time at SAP) is the impact of SOA on ERP. He avers (I think rightly) that enterprise software cannot be assembled from JBOWS (just a bunch of web services), largely because of concerns about semantic consistency and compliance.
In the past, major vendors persuaded their customers that the way to achieve semantic consistency and compliance was to purchase the entire application suite from a single supplier. While at SAP, Agassi has championed the creation of a radical SOA-based alternative to this strategy. If you build the rules into the ERP platform (e.g. Netweaver), then your chosen vendor (e.g. SAP) can maintain hegemony and control over a heterogeneous but properly architected collection of enterprise services.
Including of course the multiple inconsistent implementations of SAP software that global mergers sometimes throw up.
So what matters now, according to Agassi, is not the ERP but the ERP platform. If you are going to implement enterprise software, then use a platform that is specifically designed to support enterprise software, rather than a general-purpose software platform.
There are various other terms for this platform, including the bland (Business Process Platform or BPP) and the downright ugly (Applistructure). For recent commentary, see Sam Lowe, Michael "Mitch" Hatscher (via Matej) and Phil Windley (via John Gøtze).
Moving the platform upwards is a powerful architectural strategy, as I've argued before. But these strategies, while enabled and encouraged by SOA, remain challenging both technically and conceptually. It will be interesting to see whether this strategy goes on the back burner once Agassi is out of SAP.