Piper is getting flak from his fans for inviting Rick Warren to his Desiring God conference. Look at this video, the long version here .
Why did Piper invite Warren to his conference? Because Warren has been reading Jonathan Edwards, the Revivalist of long ago, since Piper is a fan of Edwards, there you go. This shows you that when Enthusiasm becomes the common cause, people get together. This is why Calvinism does not work because it is Enthusiastic and Experiential. It is the experience that unites rather than the confession. I wrote about Edwards' famous sermon here. Sadly the most famous sermon has only Law, no Gospel.
The more I think about Calvinism, I conclude it is shaky. In fact, I think it is a big contributor to the mess and instability that present Evangelicalism finds itself in. If you think Walther and Co. is the answer, think again. It does not solve it.