As soon as I connected with Magic Trackpad (having used MacBook Pro's touchpad) the hot corners stopped working. OSX is 10.9.3 Mavericks
For me this seems like a bug as I would want to use hot corners even with Trackpad?
CLARIFICATION 1: In Settings > Mission Control > Hot Corners, the settings are still there as they were so in that regards everything should be working. And they are when I use this MBP's touchpad, but not with Magic Trackpad.
ACTUALLY for some magical reason it started working! Without resetarting computer, that I have tried earlier already. Great although it remains a mystery as to what happened... I did dangle with trackpads settings "show desktop" on/off, thats it. Might be for some other reason.