This is actually quite serious - I thought I had a virus or something in my computer, since the screen went all strange. I don't think that ads such as these help to sell the products, because we all get so frustrated and annoyed. Pop-ups should be quite easy to close, otherwise we all get sick of the product they advertise for (hint to any multinational companies which might chance to read this...)
BTW, there is another way of closing them - click on them, then quickly close the new window that opened.