We have two! My wife bought the 2001 Mica Green and it arrived in March, 2002. We got it because my teenage kids were growing too tall to fit into the Corolla she had. There was (is) plenty of back seat space in the 2001 and even more, of course, in the 2004, which I have. It replaced a 1984 Toyota Van (which we still have for hauling stuff-but which is no longer my main vehicle). I would buy my 17 year old daughter a used 2001-2003, then we'd have three! But I understand the used ones are hard to find as well. They just keep getting better and better!
When we testdrove the Prius to replace my car last year, my husband decided during the testdrive that he wanted one too. We now have his & her's 04s.
If I needed two cars, I would rather buy something smaller. I hope that Toyota eventually markets something like the Tercel with a hybrid package. Don't get me wrong. I love my Prius. I just don't have the need for a car this size, and I put around 30,000 miles a year on it.