Is estimating a bad practice?

According to Naresh Jain, writing in response to a LinkedIn Agile Alliance discussion, it is:

Estimates are a hang-over from the waterfall world. For the last 6 years, I’ve been very happy and successful building products and delivering projects without all the estimation related ab-ra-ca-dab-ra. No more real-time, ideal-time, story point, function point; non-sense. I’ve realized the key is to focus on the flow of the deliverable and not whether your are delivering according to the estimates.

He goes on to make a pretty compelling case for the abolition of estimates (he provides some useful back-and-forth with his detractors in the comments, too). Since some of our teams have started down the kan-ban path, it would be interesting to know how much of our experience squares with Jain's claims.

Jain also references Joshua Kerievsky's Agile 2008 presentation on the same topic.