Sometimes the question is answered with "No" (without any testing), and trivial, but stateless, enterprise applications for a few users are built with a significant overhead.In the following screencast, I created with the pace of 500 HTTP sessions per second as many HTTP sessions as only possible in a trivial PoC. A HTTP session consists of a
SessionScopedbacking bean and a Stateful Session Bean with three attributes. A stateful Boundary in addition to a SessionScoped backing bean in this context does not make any sense, but wastes more memory and therefore shortens the screencast :-)
[See also an in-depth discussion in the "Real World Java EE Patterns--Rethinking Best Practices" book (Second Iteration, "Green Book"), page 50, chapter "The Extended Mode and Concurrency"], page 91 in chapter "Gateway", and page 429 in chapter "The Essential Complexity of Domain-Driven Designs".
NEW 2016: Java EE 7 Workshops: Bootstrap, Effective, Architectures, April, 4th-6th, Munich's Airport
On demand workshops: Java EE 7 Bootstrap, Effective Java EE 7 and NEW: Java EE 7 Testing are available for streaming