Now that I am actually using blog systems that support metaWeblog.newMediaObject (which I guess iPhoto2Weblog requires), I will revisit and try this. From esigler.2nw.net/software:
I got tired of the hassle involved with putting my photos up on the web. iPhoto could manage the images, but couldn't do much with them once they were published on the web. The myriad of HTML export plugins for iPhoto are all nice, but they still don't get me things like comments and TrackBack. So I built a plugin for iPhoto2 that exports to any weblog that supports the MetaWeblogAPI. It uploads the files to the remote server (via the metaWeblog API) and then creates a series of weblog posts with the linked images in place.