How can I create a variable sized UITableViewCell?

I can't seem to get the text to actually span multiple lines. The heights look correct. What am I missing?

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewCell *cell =  [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"StatusCell"] autorelease];

    CGRect frame = cell.contentView.bounds;
    UILabel *myLabel = [[UILabel alloc] initWithFrame:frame];
    myLabel.text = [[person.updates objectAtIndex:indexPath.row] valueForKey:@"text"];
    [cell.contentView addSubview:myLabel];

    [myLabel release];

    return cell;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

    NSString *text = [[person.updates objectAtIndex:indexPath.row] valueForKey:@"text"];
    UIFont *font = [UIFont systemFontOfSize:[UIFont systemFontSize]];
    CGSize withinSize = CGSizeMake(tableView.frame.size.width, 1000);
    CGSize size = [text sizeWithFont:font constrainedToSize:withinSize lineBreakMode:UILineBreakModeWordWrap];

    return size.height + 20;    
}

Also, what am I missing that makes the labels appear longer than the table cell?