Comment 33 for bug 579804

@Peter-Alexander: This feature has been implemented in trunk, is optional, and is off by default. It can currently be enabled via a command-line option, and in the next few days we'll be adding a preferences checkbox you can use to enable the feature if you want.

By the way, in Shotwell 0.9 we're planning to add the ability to flag photos. Perhaps you'll be able to use these flags instead of temporary tags. See http://trac.yorba.org/ticket/2756 .