It's a rare founder who has no offer he'd take. In fact, if you have shareholders or employees with options, and someone makes you an offer that's significantly above the expected value of your company, fiduciary responsibility requires you to take it.
You can bend this requirement to some extent by overestimating your expected value, but there is always some number you'd have to take.
They were growing rapidly and figured out the revenue game.
We have no idea how close Mint was to making good revenue, especially if lead-gen was their only source. Maybe they figured lead-gen wasn't lucrative enough and decided to take the early payout over losing time and money in the longer run?
There are many successful business that truly don't have a number they'd HAVE to take. It's a choice, and that choice doesn't appear to be actively made by this generation's poster-child business leaders.
I do disagree with Jason, I think that there are a lot of unspoken young businsses, not in the spotlight, that do have the passion to take the baton from the previous generation; it's just that they don't seek out the attention, nor does the attention seek them out.
Never underestimate the risk of losing it all because of a failure to diversify.
If you have major shareholders or they vote to take it against your wishes then perhaps. But, if you are the major 'holder or have a casting vote then you can do as you wish. Sure greed may motivate you more the bigger the numbers get but you don't have to take the money.