How many interfaces?
Read Pie's take on the problem with always going after and adding the next greatest user interface to your app HERE.
He makes a good point that while new interfaces that have something neat to offer abound, creating yet another way to access your app is not always the best use of time/money/your app.
I agree, you do certainly reach a point of diminishing returns. I think, though, this is why (micro) mashup architecture is so interesting. "Whole Cloth" user interfaces that seek to be the end all be all for everything are trendy at best, typically well-intentioned-but-ill-conceived ,and just plain suck at worst.
Portals were an attempt to bring everything together at one point. Microsoft wants SharePoint to be the single-global-user-interface-of-and-for-everything. Google is going after either the browser or desktop widgets as the global interface it would seem. But I think these, while neat, possibly useful, and maybe swoopy will eventually go the same way I predict.
Instead I tend to think that the proliferation of SOA across apps (and yes, James, possibly even cross app cross domain, cross corporation security standards) will lead to a create your own UI that allows you to build a mashup interface combining (as in Pie's example) Siebel and ECM and Google News and your supplier's discount parts catalogue with their staff directory and your AP system. I'm not thinking of Yahoo! Pipes which is more of a mildly interesting toy. But rather a yet to emerge UI (desktop? browser?) that is easy for technophobes but sophisticated enough for them to do their jobs.
Of course, software vendors will continue to create whole cloth UIs since, if we don't, we are really just selling SDKs and those don't demo as well.
