Our blind spots about validation can and do harm real users if they're poorly or incompletely thought out. What might seem like a completely rational limit to us might hurt a real user who needs to exceed that limit, through no fault of their own. How many women are "BETTYJEAN" because their first name "can't" have a space in it?

He makes a few suggestions developers can do to help the situation and get their current project's validation back out into 20-20 vision:

• Accept valid data in any form provided by the user.
• Where possible, use well-developed validation libraries.
• Do not place artificial limits on valid data.
• Do place valid limits on specific data.