I wouldn’t publish a letter to someone who has hurt me. Either I would discuss it with them or I would keep it to myself. Publishing hurt only begets more hurt: I don’t want that.
I’ve run a blog since about 1998, on and off, vaguely serving as a diary, vaguely serving as an aide memoir. I switched to Tumblr because I liked the simple interface that I saw on Dominic’s Tumblog. I may switch away from Tumblr to self-hosted WordPress at some point: I’m not using the “social” aspects of Tumblr and I’m not enamoured of “The Cloud”.