Well, to be honest, everyone will be willing to wear a free signature depending upon availability. This means that if you are not in a campaign, your signature and/or avatar is free, so wear anything for free promotion or for a social cause.
Not exactly. There are members of this forum who aren't in any signature campaigns and they never apply for any either. But they also don't seem willing to advertise things for free, so they either don't care about signatures in general, they don't think it's a good idea, or they don't want to be told what to do.
The true essence of this question should be that will you be willing to let go of your signature in order to wear another signature for free for a noble or social cause.
That's not something I expect people to do nor should anyone be asked to do something like that.