Why ban API use by applications? Wouldn't that kill a large part of Facebook's valuation? Users can turn email off for all or individual apps, and people could

Why ban API use by applications? Wouldn't that kill a large part of Facebook's valuation? Users can turn email off for all or individual apps, and people could only add apps which use their information more responsibly. I'm not a FB user, and in a more ideal situation the FB 'like' button would not be so heavy--you can't really remove it for sites because it's a lifeline, but for site performance it's slow.