Melissa Perri in Changing the Conversation about Product Management vs. UX:

Product Management with no User Experience Design creates functional products that don’t make users excited. User Experience Design with no Product Management produces delightful products that don’t become businesses.

I have a few quibbles with this article (including the idea that the role of UX is to make users excited…), but I like this quote because it ties in with a common theme I write about: the importance of combining both user needs with business goals to create successful products.