Last modified: 2011-03-13 18:05:18 UTC
For the purpose of determining which pages are actively watched, there should be a per-page timestamp that records the last time when a watchlist containing the page was viewed. This timestamp should be visible at least in page history and in the list of recently changed pages.
This would be the little cousin of individual page view counters in terms of write load, since we'd be performing one write for each watched page on an individual watchlist view, which could be a vast number. It might also not be desirable to allow this information to be viewed with such ease, in much the same vein that the list of unwatched pages is restricted to trusted users, to make it a little bit harder for vandals and other unwanted editors to figure out soft targets.