[psychonic]

MM:S and SM don't support listen servers. They might work, they might not - a lot of it depends on the game and Valve updates.

Loading any plugins, even with -insecure is broken on some game's clients, as well as the dedicated server versions that launch through the Steam client (in the Tools tab). Additionally, in many cases, if you get plugins loading on a listen server, you will get crashing on games that use Valve's CEG DRM in the client (L4D2, Portal 2, CS:GO).