Calling isValid on a translated (using Zend_Translate) increases the size of the Zend_Form instance with the size of the translation times the number of elements in the form. With a sizeable translation-file and a larger form this could easily be from under 100kb to over 1mb. Don't know how much of a problem this is, hopefully someone of you can judge this better.

The line that causes this is: foreach ($this->getElements() as $key => $element) { $element->setTranslator($translator);

/**
 * Validate the form
 * 
 * @param  array $data 
 * @return boolean
 */
public function isValid($data)
{
    if (!is_array($data)) {
        require_once 'Zend/Form/Exception.php';
        throw new Zend_Form_Exception(__CLASS__ . '::' . __METHOD__ . ' expects an array');
    }
    $translator = $this->getTranslator();
    $valid      = true;

    if ($this->isArray()) {
        $data = $this->_dissolveArrayValue($data, $this->getElementsBelongTo());
    }

    foreach ($this->getElements() as $key => $element) {
        $element->setTranslator($translator);