The first few times that I linked to my own blog in a post, or to another wordpress.com blog, a pingback was automatically generated, showing in the comments of the original post that a newer post had linked to the old post.
Lately, no pingbacks appear, on either my blog or another wordpress.com blog. This has been going for a while, probably the last few months. Options/Discussion has both the "attempt to notify linked blogs" and "allow link notifications" checked.
I use Ecto to post (on a Mac), but pingbacks used to happen using Ecto. I haven't updated Ecto, I don't think. Version 2.4.2. I did re-install it onto an upgraded machine lately. My memory is not quite clear, but I think the pingbacks stopped before I re-installed it.
I even edited some posts with links directly in the web editor (firefox mac), and pingbacks still don't appear.
I searched the FAQ and forums and learned more about pingbacks, but did not see this problem mentioned.