Selling your company only makes sense if you think they can do a better job than you can. Or when you think they’re overvaluing the prospects of your company. That’s either the talk of the meek or a con man (“let’s get these suckers to overpay for this company of questionable value…”).
Of course the trillion dollar number is ridiculous (just trying to make a point) but you can insert whatever number you want. DHH directly says you should only sell if you think the buyer can do better or if they overvalue your company.
As far as selling because you think the buyer can do better goes, does anyone actually do that? How many people are strong enough to build a company to the point where someone wants to buy it and then suddenly turn meek when the offer is on the table?
Selling your company doesn't make you a con man either. Even if someone overpays. If someone overpays, should you offer to give back the difference?
Like I said in my original comment, there is a lot of truth in what 37signals has to say, including this post, but sometimes they stretch it too far.