@BroadwayConcierge - I can definitely see how you and others would feel that way, and I respect that. I personally feel it's definitely a bit on the tacky side, but then again I actually like tacky a lot of times, and I think it still can work depending on the show. Mostly I feel it really only fits in shows that are already in that kind of tone in the first place - Urinetown and Spelling Bee, for example, or anything that's both already lighthearted and especially any work that already involves audience participation or being "meta" in the show itself. It feels a lot more out of place in more serious works like Sweeney Todd though, but I guess I can understand if they're doing it to try to keep the audience's minds fully in the setting, and especially if it's more before the show starts rather than during intermission.
It does seem like for the most part it's only local/regional theaters that decide to do this, which I kind of expected. Unless the person who cited Edwin Drood was talking about a Broadway production - I know that musical is another one that's heavy on audience interaction, so I can see it fitting for that too.