In the meantime, you can edit the usermeet.sc/plugin.xml and do:
<value>
<data key="uri" value="contact"></data>
<data key="menu_title" value="open a ticket"></data>
<data key="icon" value="images/crystal/icon_open_ticket.gif"></data>
<data key="requires_login" value="1"></data>
</value>

jlehrhoff brought this up on the forums:
http://www.cerb4.com/forums/showthread.php?p=4457

While at it, I suggest to also add an option to require login to browse the KB.

Implemented:
http://github.com/jstanden/cerb4/commit/7e3846159b927e421a765958c8003eec4527d588

Verified implemented and working in 4.2 dev build 907.

There are two new options for the Support Center, one for the 'Open Ticket' and one for the 'Knowledgebase' module. Just enable the "Must be logged in to..." options for the corresponding module.

Will update forum thread when 4.2 is released into stable.