Namespace proliferation

Does it matter that there is such a proliferation of namespaces? It seems like new ones keep getting added: Thread (for LQT), Module (for Scribunto), Book (for Collection), etc. Perhaps the adding of more namespaces should be avoided when there are only going to be a few pages in those namespaces.

Disadvantages

 * If you're exporting all the content from a wiki, that's more visits to Special:AllPages to get the complete list of pages, because you have to go namespace by namespace.
 * There are only 26 letters in the alphabet, so not all of these namespaces can have one-letter aliases (e.g. Talk:, Template:, Thread:, etc. all start with T).
 * It's more stuff to sort through when you get a drop-down list of namespaces.
 * Some implementations of features using separate namespaces clog up RecentChanges by creating a separate page for each entry (e.g. a new post to a thread).