Thing is, Liferay is about to break the ice and bring low cost shared hosting to the Java world. If this is a goal I think it needs a bit more consideration, that's why I was asking for a distinct topic.
Here is one feature I would ask for: separate databases for separate customers, as PHP hosting providers have to offer.
To fit affordable shared hosting in a dedicated server I would use only one JVM instance with access to a decent 3-4GB RAM, all hosting customers sharing the same JVM, who would rely on Java for security. In this JVM I would run a single Liferay instance (or one for each important version, like 4.2, 5.2 etc. if possible). A Liferay instance would connect to a master account database, then a level of indirection will let each account have its separate database (jdbc pool) and let each customer manage it the way it sees fit, each account with its own website instances and communities, like now.
I really don't think you can run more than one JVM in a dedicated server and keep the shared hosting offer affordable, unfortunately. So, there are some strategies to review more carefully.
