Finland’s citizenship legislation changed in 2003 to allow multiple citizenship. Prior to this, Finnish citizens who became naturalized in other countries lost their Finnish citizenship. The 5 year span from May 31st 2003 through May 31st 2008 was established to permit those who had previously lost their citizenship to regain it. The cost of filing a citizenship declaration with a US embassy is 240 euros. For those who are eligible, Finnish citizenship also affords European citizenship and the freedom to live and work in any of the member countries.
Here are some useful links for those who may be interested: