Typically when you set out to build a RIA, you look at what data you're about to keep about a persons account. In that obviously "Username, Password and Email" are three key pieces of information you need to begin. The rest is the other metadata associated to an account, and in CRM's you'd go deeper in terms of phone numbers etc.
The data is up to you and I'd never dictate what you should and shouldn't capture. What I am focused on is how you present that data, in that how "Rich" do you want the experience to be in terms of presenting what is probably the most boring data in a RIA.
I'd wager majority use Tabs + Forms and basically categories this into neat portions that are close to being semantically correct (in terms of which heading they fall under - look into information architecture).
Context is what though? What's the context of having a person(s) username & password in a form along side their other information? Isn't this more of a security thing vs a personal bio? What if you're profiling your accounts based on experience they've had with you as well? where do you put that data?
Point is, suddenly your tabbed approach starts to get bogged down and the next thing you know it, you're facing a comprehensive set of tabs (stacked ontop of one another most likely) and the form probably grows in metrics - width/height to accommodate).
Let's put the Rich back into RIA: Well, I'd now argue that if you're using some of the new RIA technologies, why the heck are you using Tabs? In that, you've got the ability to go beyond a form now, in that the technology is a blank canvas and the experience is up to your imagination (alongside some basic Usability Principals).
That's the key, why present a form which after traversing through a grid presents you with more then you bargained for. Why drop the experience there, why not approach it differently - radically if you will.