I have also received this invitation and tried it on a few images. It's also good when the watermark in placed in front of the most important part of an image - you drag it a little and this parts shows more, yet you can still protect it.
One suggestion I gave was having a preview tool. The way it is set, the image is "greyed" while you position the watermark, so you can't see the final look unless you confirm the new placement.
Regards,
Adelaide