Computerized election theft a reality?

I recently read a book making some disturbing claims about our election systems:

Points the author makes:

• Exit polls no longer are as accurate as they once were. Why?
• If you don't have a system where humans are observably counting ballots in public, various tricks can be played
• Even optical scan systems are vulnerable (just set the target to -100 and the opponent to +100 on startup and the machine balances)
• "Social issues" have tilted left recently (legal marijuana, gay marriage) but elections somehow still go to Republicans

The author is an admitted 'democrat/left-winger' but makes the point that if results were skewed toward the Democrats the way they've been skewed toward the Republicans since 2000 there would be no end of screaming ... and of course there isn't!

I found it annoyingly plausible ... the author calls for auditing of election results which seems to be all we can hope for.

What do you think?