This issue was raised in this blog on Wednesday, but I thought it interesting to posit the idea that perhaps that rather than all-free email or all-pay email, we could be seeing the introduction of a two tiered system. This is certainly the allegation that is being levelled at AOL (see this Financial Times article).
Is there anything wrong with a two tiered system? If users are prepared to pay for an email system that guarantees increased speed and authentication, why shouldn't just accept that it is their right to do so? It all comes back to the fundamental questions: should email be free, and why?