One of those 'no brainer' moves, glad to see it got done. Love the irony of a YC exit as an acquisition by a YC company :-) Congratulations, hackpad is an awesome product and the combination with Dropbox has excellent potential.
Honest question, why is that irony?
In this case it is more like having the kids grow up and being successful than anything nefarious. And YC gets to put 'acquired Apr '14' in the box of outcomes.