I could see using this architecture if each portlet is an application unto itself and did need to interact with any other portlets or any common data.
Example: the sample news and weather portlets are in separate war files because they are totally separate applications.
Also, using this type of architecture, it is fairly easy to build a custom portal containing only the desired portlets.
Of course, if there are multiple portlets that provide access to common data, those portlets should all be bundled into a single war file. An example might be a set of portlets that are used by employees to log their work time, view reports on time spent, and so on.
Yes, all the portlets are higly inter-corelated, they need to communicate and share data. And they communicate using HTTP POST requests instead of IPC ! That's probably because IPC doesn't work with separated deployed portlet ?