Lightboxes, for those that don't know, the box that is highlighted (and the rest of the screen is greyed out). Let's put aside the likes / dislikes of them for a moment, typically they are used for email capture. So things like 'sign up for our newsletter' etc. Recently I've been seeing more and more of them focused on Facebook likes rather than email.

I'm interested to hear from anyone who's trialled this approach. Was there a certain design that worked better than others, was there a certain timing / behaviour in presenting the lightbox that worked.

How did the conversion rate stack up again email capture conversion?