I've heard this a few times from RIA regulars:
"firstname.lastname@example.org is great and all, but why do I need it when I can just post my reviews from the site?"
For regular users, this is a valid point. You usually don't need need to use email@example.com unless you want to, although it is far and away the easiest way to post photos with your review, or to add new things to the site.
But here's a case study from my own experience of when the firstname.lastname@example.org feature was really, really helpful.
I recently came back from a trip to Tokyo. It was a 12 hour flight, with no wifi. So what did I do? I opened up my laptop and drafted some reviews of each of the amazing things I saw on my trip, and attached photos to each one.
When I was back online, those emails went out and posted instantly.
I use RIA almost as a diary of the things (and my reactions to those things) that I come across during my life. Reviews@rateitall.com is a way to document and capture those moments, even without access to the Internet.
This theme of how to log a moment on RIA even during those times when you are not sitting at your desk with an Internet connection is something I find pretty interesting.
For some of my Tokyo reviews, see here, here, here, and here.