But, GUEST,litchick, an increasing number of people think that it has been conclusively proven who wrote (a least the majority of) the plays and sonnets.

Do you think that Shakespeare's "retirement" as an author, but not as a producer or actor, occured by sheer coincidence shortly after deVere's death?

Do you accept the view of those scholars who say that Sonnet 6 is clearly addressed to the Earl of Southhampton?   If so, why was Bill writing a sonnet to one of deVere's closest friends, a person who Bill had never met?   

And so on.

(There is masses and masses of stuff like this - no one single piece is conclusive in itself, but the sheer weight of all of them makes, to me, a compelling case).