In an interview with Windows IT Pro, VMware President Diane Greene said the company believe virtualization be more and more focused on the concept of virtual appliance:
…
Because of VMware’s extensive experience with virtualization–a key reason its technologies are more advanced and capable than Microsoft’s virtualization products–Greene says that the company has a better grip on where virtualization is going in the market.It’s not about virtual environments any more, in which a customer runs Windows or Linux in a software sandbox. Instead, virtualization is moving toward application appliances. “It’s about the appliance, not the OS,” Greene explained. “Microsoft is just tying its Hypervisor technology to the OS and to the underlying hardware required to run Windows.”…
Read the whole article at source.
Virtual appliances are another way to deliver software as a service, partially competing with application virtualization and streaming approach.
In facts while application virtualization is the best fit for distributing a one-program solution, when we have to deliver a solution made of several applications working together virtual appliances seem a better choice.
In the end I would call virtual appliances approach service virtualization, and wouldn’t be surprised to see VMware working at (or acquiring a company involved in) streaming technologies a la Softricity, Stream Theory, AppStream, etc.