The same idea was used by COOP Italia, a famous supermarket chain, to invite people to sign a petition to admit the sale of drugs by the supermarkets.
The claim of that campaign was (more or less): sign to lower the “fever” of prices (= too high prices).

This adv was done by Saatchi & Saatchi, but i’m not too sure about that..

via
http://www.spotanatomy.info/index.php/2007/05/21/campagne_wwf_acqua_ombra_termometro

I think of all their ads, this one is by far their worst.

On first glance by about 20 people I showed it to, every one of them read it as this:

No one’s willing to sign up to stop global warming until the temp drops.

Once you stop to really look at it you kinda get the point.