This is a pretty big problem with a lot of people at my workplace. One guy initiated a conversation with me when we were side by side at urinals. When he was done pissing, he turns so he's 3/4 facing me, still right next to me in front of his urinal, and keeps talking, prompting for acknowledgment with things like "Right aDam?". Very annoying...
The worst is the continuing conversation from the urinal area to the stall area that I've entered. Okay let's wrap this one up because I would prefer not to keep having you talk to me while I'm SHITTING IN THE TOILET!!!
One manager around here once followed someone into the bathroom looking for him, saw he was in the stall taking a shit, and initiated a conversation about something work related...