Link to Don Dodge's post:
http://dondodge.typepad.com/the_next_big_thing/2012/04/why-instagram-is-worth-1b-to-facebook-web-20-just-went-mobile.html
Here's a link to yesterday's post on the rationale behind Facebook's acquisition of Instagram: http://www.allenlatta.com/1/post/2012/04/the-rationale-behind-facebooks-acquisition-of-instagram.html