www-client/mozilla-firefox-3.6.0-r2 requires that secure deletes be done in SQLite. While this is a good security feature, SSDs that support TRIM already render deleted data irrecoverable and zeroing data before deleting it accelerates the death of all SSDs.
Currently, it is difficult to avoid this ugprade because www-client/mozilla-firefox-3.6-r1, along with net-libs/xulrunner-1.9.2-r1, have been removed from portage and adding the r2 versions of them to the package.mask file will result in portage attempting to downgrade them, which essentially breaks portage for those that wish to avoid this feature. It also ruins the outlook on future upgrades for those that wish to avoid this behavior, as there is no prospect of an ebuild being available that has no secure delete functionality.
I recommend that either a secure-delete USE flag or no-secure-delete use flag be added to mozilla-firefox to enable owners of SSDs to disable this feature. It probably would be ideal to have a secure-delete flag that firefox toggles automatically when -secure-delete is not specified, but if that is not possible a no-secure-delete flag would be the next best option. Having not made ebuilds myself, I am not sure if the ideal case is possible.
*** This bug has been marked as a duplicate of bug 304913 ***