If the backslashes don't do it, then what?

[...]
foo: ('lorem ipsum dolor sit amet'),
bar: ('lorem ipsum \(dolor\) sit amet'),
[...]

Here's the full code:

google.load('orkut.share', '1');
google.setOnLoadCallback(function() {
  new google.orkut.share.Button({
    title: 'foo',
    summary: ('foo \(bar\) foo'),
    thumbnail: ('...'),
    destination: '...'}).draw('orkut');
});