WordPress appears to continue with execution even when MySQL refuses connections/queries after init. Here’s a comment in the MySQL docs suggesting how to detect the condition in raw PHP:
$link = mysql_connect("localhost", "mysql_user", "mysql_password");
if (mysql_errno() == 1203) {
// 1203 == ER_TOO_MANY_USER_CONNECTIONS (mysqld_error.h)
header("Location: http://your.site.com/alternate_page.php");
exit;
}
Just a note to myself, but I wonder if there’s opportunity here.