In bug 388332 comment 27 aravind said that the cloned repos wouldn't be browsable via HTTP... and I think there was a misunderstanding about what that meant. It is important that anonymous users be able to clone/view these repositories via HTTP. It is not important that the root page at http://hg.mozilla.org list these repositories. This is needed in order to get the try server working properly, which clones anonymously via HTTP.
User created repositories are now available on http. The url is http://hg.mozilla.org/users/ Please open IT tkts if you notice anything weird with the web interface.