Why are the Polls so Crazy?

Why do John Zogby's polls swing so violently? Why are they so volatile? First, it is clear that the pollsters suck (witness the inaccuracy of exit polling in 2000). Second, I think that there is another reason why the polls are swinging so wildly.

I think that in this election, there are a lot more people who are "undecided" than there are people who admit to being undecided. I think this for several reasons:
1) Amongst intelligent voters, there is no obvious choice. Both candidates have real appeal.
2) This campaign season has NOT been about the stereotypical "issues." Neither candidate is talking about abortion, crime, education, or any of the other typical hot-button issues very much, because their positions on these things hardly differ. The only issue that has come up repeatedly is tax. McCain is on the populist side of this issue (he's generally for lower taxes than is Obama).
3) Neither candidate has positioned himself as "the religious choice" which means that people who just vote for or against such candidates don't have a straightforward way to choose.
4) Much of Obama's support is from young people and other groups whose turnout is very uncertain.
5) Much of McCain's support is from religious people who don't particularly like him and may not turn out, either.

I have seen Obama with leads anywhere from 4% (statistically, barely significant) to 15% (which would be the biggest landslide in recent history) in the course of about 2 weeks. That seems weird to me. Nothing interesting enough has happened to actually change peoples' minds that much, unless their minds weren't really made up in the first place.

Any lead of less than about 8% or so for Obama could still end up being very close, due both to the Bradley effect and to the uncertainty of turnout.

I suspect that this election will be far closer than people think. If I had to bet, I would still bet that Obama wins, mostly because of people casting their votes "against" the party in power, whom they blame for the current economic conditions. The irony of this is that it would give the democrats both the Congress and the White House, which is generally the worst possible recipe for government spending and deficits.