The article can be read here:
http://www.washingtonpost.com/lifestyle/travel/are-postcards-a-thing-of-the-past/2015/02/26/a243909a-b945-11e4-aa05-1ce812b3fdd2_story.html
But, I will add this. Personalized postcards can be sent while on trips, using your own photos. Instead of posting something to your blog, you just make your own postcard and send it via email to a specific person. It is not so hard, and still arrives almost immediately.
One example of this, is an e-postcard I sent to my son, while on a trip to Costa Rica.