Oracle supported linux distributions According to this site (http://www.dbspecialists.com/oracle11glinux.html), Oracle is only supported on the following Linux distributions:


Oracle Enterprise Linux
Red Hat
SUSE
Asianux


Is there any technical reason that Oracle would perform poorly on a Debian-based install (Ubuntu)?  Or is this more about dealing with Oracle from an enterprise support standpoint?
There is no reason why Oracle would perform badly on Ubuntu (though Oracles OEL kernel has some Oracle-specific optimisations), it's all about enterprise support.

Certification is an expensive and time-consuming task, as is training support workers in each flavour of Linux - that's why the RDBMS is only officially supported on a select number of releases.