Is it always necessary to exclude cglib when using hibernate-entitymanager?

Question

A lot of time was spent setting up my project and finally finding out that I should exclude cglib from my dependencies:

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>3.6.4.Final</version>
    </dependency>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>3.6.4.Final</version>
        <exclusions>
            <exclusion>
                <groupId>cglib</groupId>
                <artifactId>cglib</artifactId>
            </exclusion>
            <exclusion>
                <groupId>cglib</groupId>
                <artifactId>cglib-nodep</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

Should cglib always be excluded? Why is this not ruled out by default? And what's worse, why doesn't the Hibernate white paper say anything about this?