S2 slaves were hit by a storm of these on svwiki:
SELECT /* SiteStatsInit::edits 127.0.0.1 */ COUNT(*) FROM revision LIMIT 1
Then minutes later a very similar storm of these:
SELECT /* SiteStatsInit::articles ... */ COUNT(DISTINCT page_id) FROM page, pagelinks WHERE page_namespace = '0' AND page_is_redirect = '0' AND (pl_from=page_id) LIMIT 1
The queries cam from wikiuser and various client IPs, implying they were not run from any maintenance script or job. Clients did include a lot of msnbot and googlebot, but not exclusively.
Both queries should be run asynchronously and cached somewhere (which based on IRC conversation between hoo/Nemo/aude, is actually the expected behavior).