He can't be with the conspiracy, because they have a limited tolerance for BS and would kick him out.
He can't be Osama, because the bandwith in your average cave isn't large enough to handle the sheer volume of BS he posts.
He can't be in our imaginations, because a mortal mind couldn't cope with all of the BS that would be floating around his/her head.
He can't be with Vauxy, because he already has an intimate (online) relationship with myself. No BS.
Therefore, with my totally zetetic reasoning, I conclude that Tom Bishop is GWB. More specifically, the immortal alien mind who is impersonating our beloved US President.