$("input.tr_clone_add").live('click', function() {$(this).closest('.tr_clone').clone().insertAfter(".tr_clone")});

<table width="100%" border="0" cellspacing="0" cellpadding="0" id="table-data">
<tr>
<td>Name</td>
<td>Location</td>
<td>From</td>
<td>To</td>
<td>Add</td>
</tr>
<tr class="tr_clone">
<td><input type="text" autofocus placeholder="who" name="who" ></td>
<td><input type="text" autofocus placeholder="location" name="location" ></td>
<td><input type="text" placeholder="Start Date" name="datepicker_start" class="datepicker"></td>
<td><input type="text" placeholder="End Date" name="datepicker_end" class="datepicker"></td>
<td><input type="button" name="add" value="Add" class="tr_clone_add"></td>
</tr>
</table><!-- /table#table-data -->

.insertAfter(".tr_clone")

var $tr    = $(this).closest('.tr_clone');
var $clone = $tr.clone();
$clone.find(':text').val('');
$tr.after($clone);

$( table ).delegate( '.tr_clone_add', 'click', function () {
    var thisRow = $( this ).closest( 'tr' )[0];
    $( thisRow ).clone().insertAfter( thisRow ).find( 'input:text' ).val( '' );
});

$(table).on('click', '.tr_clone_add', function () { … });

$(".tr_clone_add").live('click', CloneRow);

function CloneRow()
{
    $(this).closest('.tr_clone').clone().insertAfter(".tr_clone:last");
}

var $tableBody = $('#tbl').find("tbody"),
$trLast = $tableBody.find("tr:last"),
$trNew = $trLast.clone();

$trLast.after($trNew);