Basically, the article should've been titled "It All Changes When The Startup Is Making A Lot Of Cash". Supposedly Groupon is making nearly $2 billion a year in revenue. The decision to turn down an acquisition has more to do with "we're a real company making a TON of cash and we don't need to sell" than the founder thinking about their legacy.
What's the point of an exit? Mostly it's to get a gigantic payday. If your startup-turned-cash-machine is already making a ton of cash every month, the founders are already getting a payday... all the time.
If you're already making FU money from the revenues of your business and someone offers you more of it, the benefit of the FU money is you can say FU to the offer.