RK> getting all namespace IDs, iterating over them and calling list=allpages RK> for each of them is quite painless. It's not worth going through a lot RK> of trouble on the server side just to make life on the client side a RK> tiny bit easier.
Anyway, just like $ ssh example.org who $ ssh example.org ps aux $ ssh example.org last can be bundled to $ ssh example.org 'who; ps aux; last' or even $ ssh example.org <<EOF ... there in general should be a way __with one request URL__ to pack an unlimited amount of operations in, and get all the results back in __one reply__. Need some temporary storage $variables too. Hmmm, not exactly "just "su nobody" and do what they ask in the maintenance directory :-)".
RK> You could of course request that such a feature be added to Special:Export http://bugzilla.wikimedia.org/show_bug.cgi?id=9474
RK> Special:Export could just provide multiple dumps, each one RK> containing a portion of the wiki (cf. [[Special:Allpages]] at enwiki).
For monster wikis probably the current Special:Export category helper button is the only way to go, as any larger slices of the wiki are probably mistaken slices of death for the user's modem.
However on small wikis (triggered by a check of some $TOTAL_PAGES, nah, or better a new $wgWelcomeToDownload (default=false)) there could be:
We're serious about openness. Welcome to download this whole wiki in portable export format. Namespaces desired: [*]Main [*]Main Talk ... [ ]Mediawiki... (boring, not checked by default)
Filter rules: [___] Limit: [10] pages. Max 250. [*]Save to file []Browse as plain text http://bugzilla.wikimedia.org/show_bug.cgi?id=16963 P.S. http://bugzilla.wikimedia.org/show_bug.cgi?id=9889
However, as I don't really "have only one burnin' desire" (http://www.mp3lyrics.org/j/jimi-hendrix/fire/) about these features I'm recommending, I'll just er, like fade away for now...