Notwithstanding the comment in CONF-2779 (XMLRPC clients are expected to do their own validation)

If I create a space using the XMLRPC interface with an invalid space key of CRAZY-SPACE, the space is still created. If I know the page names etc, then I can go and view those pages, however there are big chunks of functionality that don't work. Looking through the log, errors of the following type occur:

14:15:52,704 DEBUG [SimpleDisplayServlet] Failed to parse path /CRAZY-SPACE
java.text.ParseException: Simple path: CRAZY-SPACE could not be translated
at com.atlassian.confluence.servlet.simpledisplay.SimpleDisplayServlet.parsePath(SimpleDisplayServlet.java:89)
at com.atlassian.confluence.servlet.simpledisplay.SimpleDisplayServlet.doGet(SimpleDisplayServlet.java:42)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:358)
...

It would seem to me, that in the best interests of overall Confluence health, an invalid space should not really be creatable via XML-RPC or any other interface.

This is not a showstopper, or even really a "bug" if you consider the XMLRPC interface to be an admin only interface that lets you do dumb things. It's just something worth considering.