Pop-up ads, those unsolicited messages that sometimes pop onto your computer screen and block the site or information you're looking for until you close or respond to them, are inexpensive to product and cost nearly nothing to send. But they are so annoying to some computer users that dozens of special programs have been written to block them from appearing on the screen during Internet use. Do you think that because they are unsolicited, pop-up ads are intrusive? Are they an invasion of privacy or just savvy marketing? Explain your reasoning.