I wrote the first closing on this location when it was Mangia! Mangia!.
Shag Bistro opened not long after Mangia! closed, and while I never went there, I got the impression that it was an attempt to establish a place with more mass appeal than a somewhat upscale Italian restaurant. The name suggests something very casual and beachy, or at least the Shag part does. I've never been entirely certain what Bistro is supposed to connote in a restaurant name, but inasmuch as I have any impression, it goes in the opposite direction of casual and beachy.
Why didn't I ever get to Shag Bistro? Well, it's pretty much the same reasons I only got to Mangia! Mangia! once: location and presence-in-mind. That is to say, it's an awful long way to drive, and I usually would forget it even existed.
Of course, it's not a long way for people already in the area, but I suspect both Mangia! and Shag were just a little ahead of their time. I think everyone expects the metro area to hit Pontiac at some point, but while it might have already happened in the old economy, I suspect it will still be a while before the recession passes and the metro area starts building out again. The move of the Verizon call center from Richland Mall to Spears Creek will probably help area restaurants, but I guess it was too late for Shag.
(Hat tip to commenter Cheryl)