Where art thou from, Mitochondria?

At a Darwin vs Design conference at Southern Methodist University the other day, some protesters held up a banner asking “Why do the ribosomes (protein synthesizing machinery) in our mitochondria match those of bacteria?”. William Dembski has two major points to make against this banner:

1. ...the more interesting question for me is what causal powers were required to produce ribosomes in the first place.

This is, of course, a very common IDist type of question which is usually followed by a certain type of statement. E.g., since science has yet to produce a satisfactory explanation of something complex (the question [that actually doesn't read like a question the way I wrote it - never mind]) it automatically means that something intelligent designed it (the statement). Nothing new under the Sun here.

2. Since I’m happy for the sake of argument to allow common descent, ... But the poster, even taken on its own terms, is problematic. Eukaryotic, prokaryotic, and mitochondrial ribosomes are all quite different (see here), and it’s not clear whether mitoribosomes, as they’re called, are closer to prokaryotic than to eukaryotic ribosomes by any reasonable metric. In any case, to say that bacterial (prokaryotic) ribosomes “match” mitoribosomes seems false on any reasonable construal of the term.

Interestingly, the link he provides has no sources after 1996, which means a 1998 paper that examined various DNA sequences found that the alpha-protobactrium Ricksettsia had the best match to mitochondria. Was it a "match" (as required by Dembski)? It was the best match that had been obtained so far. Given that Dembski is happy to allow for common descent I would say that that makes for a reasonable metric.

Additional:
Even though the protestors seemed to think that the question "Why do the ribosomes (protein synthesizing machinery) in our mitochondria match those of bacteria?” was evidence against ID, this is NOT the case. In fact, no possible observation can count as evidence against ID - and this is, of course, why ID is totally vacuous.