In France, where a 75% tax rate was just put into place, some have discussed leaving in the past few months. (e.g., see here.) More recently, one announcement stunned me. Nicholas Sarkozy thinks of leaving France after 75% tax rates put into place. This is the former president! Any president/former president wanting to leave their country because of tax rates is amazing. I think it's unprecedented, but I'm not sure.
In the US, one of my favorite golfers, Phil Mickelson, made comments about potentially moving from California. They imposed new tax rates in the November election. That, along with already high rates and a terrible climate for businesses, makes the move seem logical.
Tiger Woods stated that he did leave California because of taxes.