I’m still experimenting with my whole system, and I just tried a new thing with the SNAP plugin. It adds a new function under the “New” menu called “New Post to Social Networks.” If you use it, it will create a tweet/status and send it directly to all the selected networks. It won’t create a blog post, so that defeats the POSSE goals and prevents it from having a place for the activity to gather.
Still, it is an interesting option to have available. It means you can use your blog as an all purpose interface for all of your connected networks. If there is an ephemeral thing you want to push out to multiple places simultaneously and not keep a blog record of it, you can do it that way.