>>So you grab some additional info once and only send correct info back to the business object.

Once per what? per app, per form instantiation, per add/edit?

If dealing with web-browser front-end, it's a very different situation, since HTML, perhaps with JavaScript for validation, or DHTML for better formatting, is constructed somewhere in the middle tier area, but is really a part of user interface services. Kind of messes up the standard 3-tier diagrams.