firstly do you have a robots.txt to control the search engines? If not get one!
try googling for you site too, and check the content google has for you.
Apart from that, like everyone else tiki permissions will keep you safe.
If your not on CVS then goto http://mods.tikiwiki.org click Guides and read the secure your tiki one. it talks about removing things that could be used against you. Well they could always download tiki for themselves, but your removing all the information from under there nose.
You might also want to use a apache directorymatch to prevent people from browsing db/ templates/ templates_c etc.
yourthemename can be got through the CSS path
All your hard work creating your sites templates are there for the grabbing!