The vast majority of users are interested in what edits are made by others to their user page and user talk page. They should be watching both by default, which for some reason is not the case now.
I brought this up on the editor engagement mailing list (http://lists.wikimedia.org/pipermail/ee/2013-June/000488.html) and so far there is agreement that the sane default is to have users watch their own user page and user talk page. No one so far has brought up a common case where you wouldn't want to, especially as a new user.
I would recommend we simply turn this on for all, and I'll commit to making necessary announcements on the mailing lists, in the new Tech News newsletter, etc.