While signing up for online bill payment for one of the services I use, I encountered the following check box:

Uncheck this box if you do not wish to receive electronic communications from XYZ.

This is not simply a negative-sense checkbox; it's a double-negative-sense checkbox! What's wrong with this:

Send me electronic communications from XYZ.

Oh, right, I know what's wrong with it: It's too easy for people to opt out! Marketing is all about making users ask for something they don't want.