assuming that this is a new intel machine, it won't succeed installing it natively.
You could do it in parallels, vmware or whatever vitualization package you prefer and install in in linux.
Native intel mac support for the database server will come soon.
Native intel client is already available and it works ok. (you might need to re-install the os software since on the pre-installed software are some problems with libraries that are corrupt (upgrading to 10.5.6 also works))
if you want to run an oracle database on an intel mac now you will need to install it in a virtual machine. There are plenty solutions for this available right now. Jdeveloper runs natively on a mac (both intel and ppc). Here is a nice blog <http://andrejusb.blogspot.com/2008/08/jdeveloper-11g-on-mac-os-x-leopard.html> that explains a bit how to make it work. If you follow the instructions you have a database running on linux in vmware and jdeveloper native.