DCTs post match info on the grad listserv as standard practice in my program. It is odd to do it via Facebook though, although not necessarily violating any rules.
I will say, not sure if this is also about omission indicating not matching, but everyone in my former program would know who's applying in the program in a given year and who didn't match via omission because we had small cohorts (5-7 or so) and we worked/socialized together. There was just no way to not know, but it was part of the process. Perhaps with cohorts as big as 30-40, not everyone would notice a few omissions.
I think I'm a bit confused about why this would be concerning unless there's a concern of embarrassment of the information being shared or omitted. I'm not sure what would happen if you asked your DCT in advance to not have your info shared, but you could ask and see, but it would be strange to NOT be included if you matched alongside your colleagues because our program liked to celebrate students' successes after they'd worked so hard.
It definitely sucks when folks don't match, etc., but those who didn't match in my program took it in stride and matched at phase 2 or applied the next year and matched...with the DCT announcing their successes later via the listserv to celebrate.