I see the point of this but I'm still weary of centralising a P2P solution. I think firstbits and btc.co are both valid ideas to resolve this.
But in most cases, there is no centrlalization. You are already communicating with the receiver via his website in many cases. There is no loss of privacy by also using this channel for requesting a payment address.
Do you consider e-mail a problem because it is centralized? You can switch to another mail provider if you don't like it. You could even run your own if you're paranoid. It's exactly the same here.