What are the design consideration questions in determining where to place the business logic in a Java EE application?

What are the design consideration questions in determining where to place
the business logic in a Java EE application?

Specifically, the EIS (database) Tier versus using the Web tier with
POJO's and a light framework or the standard business logic tier using
EJB's. Also, there may be other options besides these that I'm not aware
of.
My impression is that there should be some basic guidelines as to how this
should be structed in an application and it couldn't be always one over
the other, like use the database or always use EJB's since I worked with
applications that have used all three of these structures, but I never
thought about what design guidelines should I use in making the
determination?