On http://shop.lego.com, while trying to check out, I got to this UI for filling out my account information:
Guess what, folks... my first name is initials. The only place you'll see or hear "Kathryn" is when my mom is very angry at me, or on my driver's license.
It had no impact, either - the order went through just fine even though I (gasp!) used initials. What a waste of space to try to enforce such a rule in the UI.