This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
You can certainly inject EntityManager into your bean class and not bother with a DAO. The counter argument is that the DAO is still needed as it provides a single interface to the client by encapsulating data access logic.
If you will go with the DAO option ... your bean method will obtain an instance of the DAO class (possibly via a factory) and invoke the DAO method.