In the state of MD there has been a lot going on with this issue. Based on unpublished court decision in 2007 in MD, the MD Wage and Hour changed the rules to say that even if you had a policy in effect saying you did not have to pay out unused vacation that you must now pay it out. Employers went nuts, so during the General Session, the MD legislators enacted Senate Bill 797, that allows employers to pay or not pay dependent on a policy that they have distributed to all employees. Your information was correct until this law passed.
Below is an article related to this. It is in the April 2008 edition. (As a side note, you may want to sign up to receive this newsletter. They typically have some good info related to MD).
http://kollman-saucier.com/newsletters/April2008.pdf
Let me know if you need more info on this.