When publicizing new Posts via the JetPack Publicize feature (e.g. on twitter), but not using wp.me shortlinks, JetPack prefers the "raw" guid-parameter link (?p=1234) over the permalink (e.g. /2013/04/perma-link-to-post.html).
I don't think this is "expected behaviour" - Yes, the guid-parameter version is shorter, but that doesn't matter... On Twitter, there is a character limit, but hyperlinks are always 25chars long (I guess), as they shortlink the URL via t.co anyways.
The Result: Not using wp.me, publicize uses the guid-link. On Twitter, users will access the hyperlink, going from t.co to the guid-link, this one redirecting to the permalink (if enabled).
Or in a nutshell: ugly and inefficient.
I wasn't able to actually determine the function causing this in jetpack's sources, so I don't know if it's jetpack doing this, some wordpress core-function or the wordpress.com publishing-service application.
Any idea where this comes from, or better: how to change it?