While I really love how much Telltale participate in their forums (fora?), they're not exactly the only ones.
At least Caravel Games (Deadly Rooms of Death, DROD: Journey To Rooted Hold, DROD: The City Beneath), Nadeo (Trackmania/TM Sunrise/TM Nations/TM United), Bioware (Neverwinter Nights, Jade Empire et al.), Obsidian Entertainment (Neverwinter Nights 2), Epic Megagames (Unreal, Unreal Tournament et al) frequent their own forums quite a bit...
But yeah, the rule of thumb is "the smaller the company the more likely their employees participating in their own forums".
Sorry, just had to get that one off my chest.
np: Justus Köhncke - Yacht (Safe And Sound)