Hariharan put together a good list of reasons that support the decision towards an SOA:
- Long-term vision and business strategy to align your business process and IT systems
- Aquisitions and Mergers
- Modernize your IT infrastructure and business systems
- Quick changing Business Processes
- Integration of Silos
- Standard based approach
- Decouple your application business logic
- Best ROI for your IT investment
- Interacting with many third party vendors and partners
- Better control managing your service infrastructure
