In 2004 I believe it was, I signed up with Zogby as a Democrat from New Hampshire, and proceeded to answer every Internet “poll” as the rock-ribbed conservative that I am, and I know that others did the same (especially liberal Democrats who pretended to be Republicans). So even when Zogby weighs the responses so that the sample is X% Democrat, etc., it still is a phony result. Zogby Interactive is as unscientific as it gets.
Even without Republicans signing up as Democrats and vice-versa, the poll still rests on the assumption that people who voluntarily and without solicitation sign up for an online poll are going to vote in the same proportions as voters in actual elections. The bias is obvious even without respondent deception.