Via PrestoPundit, here is a radio segment from the John and Ken show featuring Cal State Los Angeles Professor Jennifer Walsh, who has done a study on the effectiveness of Three Strikes called Tough for Whom?
Prof. Walsh concludes that the law has been very effective in targeting the right people. She also mentions a very important point that I have made before: Three Strikes actually saves money, by preventing crimes that would cost society millions. At the very least, these savings should be considered as an offset against increased prison costs.
Finally, she makes a fascinating point that I have overlooked in this discussion: many people serving second-strike sentences are actually third-strikers who already received leniency from a judge in the form of having one or more of their strikes stricken. If the law is interpreted to apply retroactively to second-strikers, then these people will end up getting two breaks — the one they already got from a judge, and a second break from Proposition 66.