I might just start a heated debate with this one. The topic is that X10's $80 wireless video camera "pop-under" ad you've probably noticed recently. The ad slips clandestinely onto a Web surfer's PC and remains unseen until the surfer closes down browser windows. Then the pop-under ad becomes visible, filling most of a computer screen. As a story in the Saint Paul Pioneer Press today puts it, pop-under ads are "just one of many alternative ad forms that advertisers are experimenting with these days as they try to punch up the impact and effectiveness of online advertising. To …