Google offered to buy Groupon for $6 billion which was turned down. Adwords belongs to Google and Groupon heavily uses this to advertise their services locally.
Hypothetically, if Groupon won't accept Google's offer, Google could turn around and say, "fine, no more advertising your business on our adwords platform." Followed up by their famous Google Ban cut and paste email summarised as "We have the right to not accept advertising based on our discretion. Our privcy policy allows us to not disclose why."
That's Google telling Groupon, "Don't make an enemy out of me, or I will squash you like i did to 100,000 advertisers. Work with me or no LOCAL advertising for you."
Except this time, Groupon has the financial muscle to swing back. Just like China smacking Google down a few notches and forcing Google to heavily reinvent their search for the China market, much to Google's dismay.
Ah well… inception scenarios over… time for us to start selling online.