I'm not for sure whether to give this a +1 or -1. Pretty TL;DR here.
+1 for the fact that it would give forum goers a chance to communicate without needing to use posts, PMs, or the TeamSpeak server, but I say if it were to be implemented, have it be moderated, if it was found on the home page of the forum, people going in there and doing things like dropping N-Bombs or posting NSFW content would more than likely turn people away from wanting to use the forum on a regular basis. What'd be nice though, also if this were implemented, having seperate boxes, one in General for discussion, shooting the shit, etc, possibly one in TF2 to discuss TF2 related stuff like SFM, Comp TF2, etc, a box in the Trading section so people could just talk with other traders online instead of combing the section for a thread about and item the need to buy or sell, and a box in the Support section for people to relay messages about server griefing, racists, server problems/crashes, and hackers much faster than making a report or adding an admin.
-1 for the fact that it would need to be moderated of course, as I stated before. How would actually fit with the theme of the forum is unknown, so it may just look ugly and out of place. Another reason is that out of the 350+ people on the forum daily, 250+ of those are guests passing by, and the 100 or so actual members, a good 40-50 use just the trading section, leaving only a small population left that actual participate in forum going and forum posting, most of which use the Skial TeamSpeak server as a place to hang out, so the boxes would more than likely end up being empty 90% of the time.