Google could build it for sure, but they can't have any guarantees that it won't turn into a failed Wave or Lively. They already have coupons for local listings

Google could build it for sure, but they can't have any guarantees that it won't turn into a failed Wave or Lively. They already have coupons for local listings ( http://www.google.com/local/add/coupons http://www.google.com/local/add/coupons , Google sign in required) and I don't see that anywhere near as popular as Groupon. On the other hand, their ad business could benefit greatly from a coupon/promotion system that actually works. They already have advertisers pouring in billions of dollars, just imagine the leverage of owning the world's leading coupon platform as well --they just need to improve revenue by 10% or so and you have 0.5 billions more each year, which is enough to justify the 5 billion price tag.