There's a number of siege queues with banned players in which have stalled. I'm currently not playing Humper on Yellow 14/14 so there's another fortnight's wait before I can time him out, and on the orange 21/3 the queue has stalled due to neither of the players starting it.
I feel that there's no reason that the games shouldn't start immediately - if you've gone after a siege board you have to expect to play. Also banned players should be removed from siege queues when they are banned to prevent this.
The other thing I want to ask is is there an ettiquette about who you should challenge in sieges. I got most of my siege boards by beating players with lower ratings and am going on a 'don't take more than one board off any player rated less than me' basis (assuming I remember). On the other hand there's always 2000+ players prepared to take a board off me so why feel sorry. What do people think?