I think you've got that backwards. Google are the ones who will probably regret lowballing Groupon. Google's track record in social anything is abysmal. What makes this half-assed attempt any different?

What Google's entry into this market means is that it will basically kill off any other Groupon clones, and merely solidify Groupon and Living Social's dominance.

This isn't social in the same sense as their past failures were though. Orkrut, Buzz, etc all relied on your friends also using those services. Crowd sourced coupons don't have this holding them up.