Currently it's only possible to define a general folder where spam mails should be moved to. This is not practicable if you use several IMAP accounts. So it sould be possible to define the spam folder for each account.
I will be grateful if this feature will be integrated. It's a strange behavior to move spam mails from one mailbox to another.
Moving the spam-folder to an account level affects all spam plugins and the core, not only Bogofilter, hence changing the component to "Other".
There's yet another request for this, this time via the Spamassassin plugin: