If I log into a console tty, run this command, startx & to run X11 in the background, and then log out of the console tty, then in the X session I no longer have the access I need for device files such as /dev/cdrom and /dev/kbd. It seems that when logging out of the tty console, if there are no other tty consoles left with me logged in, it reverts ownership of /dev/cdrom and /dev/kbd back to root again instead of leaving them in my name for the sake of the X session. The upshot of this is that when this happens I cannot run any CD player, I cannot mount CD-ROMs, and I cannot adjust the keyboard repeat rate. If I log back in to one of the console tty's and just leave it at the prompt, then these things work again in X. This may be affecting more than just /dev/cdrom and /dev/kbd. Those are just the files where I noticed the problem. I think it likely that there is a set of device files that are re-assigned when a user logs in and logs out, and they are probabably all affected by this, but I don't know enough details to tell if this is the case. This is a security problem because it means I have to leave a console logged in to make X work properly, and when I do that, even with the screen xlocked someone can still come by and hit ctrl-alt-F1 and get to my logged-in prompt. I suspect that this isn't a problem for people who run X11 via an xdm login, but I don't always want X running at all times, so I don't do that.
The problem with leaving devices ownership of console devices alone when you log out is that the next user logging in won't be able to use them. I suspect what you really want to do is "exec startx" at your console prompt.