When my company is hiring, and we lose a candidate like this, I often send emails that are similar, "Sorry to hear you're not accepting our offer. Can I ask why you didn't choose us?" This is actually the potential hire's chance to pay me a compliment, give a small amount of feedback, and keep the door open for the future in case their other "better" option falls through.
I think this blog shows a terribly self absorbed reply. My response to receiving this would be to forward the reply to my team and say, "Glad that didn't work out for us... Blessing in disguise. See below."
Know your audience. Remember, the person you're emailing works there, so you're essentially telling them that their job and work environment sucks when you write something like this.