I think I know what you are talking about, but I may be totally off, because this is what I see when browsing Audiogon. The pop-ups you are seeing is advertising. Phishing is generally referred when the site asks you for your Personal details, bank/credit-card information etc. Of late on audiogon, I have been seeing advertisements "drop-down" from the top or "creep-up" from the bottom. And sometimes there is a box in the middle of the screen with a X button to close it (just like on smart phones). I believe this is how Audiogon makes money.
Many other sites also employ these techniques to generate revenue. These are based off the recent search you might have done or some other cookies on your computer.